The two main planting periods are spring and autumn. There are certain advantages in early autumn planting if it can be done while the soil is still warm. The plants can make growth and become well established, thus ensuring a reasonable display in the first spring and summer after planting. If it cannot be done before the soil becomes wet and cold it is as well to delay until the spring.
Alpine plants supplied by nurseries are always pot-grown and, if necessary, planting can continue during the summer months, although it will be necessary to water them and even shade them from the fiercest sunshine until they begin to take root and are able to seek their own moisture.
When alpines are knocked out of the pots or other containers for planting they will be found to have a firm rootball, If this is hard it should be gently pressed and loosened, without breaking it to pieces, before it is planted. Plant very firmly. Ideally the soil in which to plant should be just moist but not really wet. Do not plant in dust-dry compost, or in any which is saturated. After planting give the plants a really thorough soaking, using a finerosed can. This settles the soil nicely around them and provides them with moisture until the roots begin to seek for it further afield. Watering Once plants in the open are firmly established watering should never be done unless it is absolutely necessary but, if, in a prolonged drought it has to be done, then do it very thoroughly; preferably in the evening.
When areas have been completely planted, and especially those occupied by the smaller, possibly cushion-forming plants, it is a good plan to top dress the whole area with small stone chippings, ensuring that the chippings are inserted beneath the foliage and close against the collar of the plants. This top dressing retains moisture in the soil, discourages the ravaging slugs ar d imparts a nicely finished appearance to the rock garden.
Plants such as the cushion phloxes, helianthemums, aubrietas, arabis, alyssums, dianthus, veronicas, hypericums, iberis and geraniums benefit from being cut back quite severely after they finish flowering. This encourages new growth and often results in a further flush of late season blossom. It also maintains a tidy habit and prolongs the life of the plants.
Normal maintenance and cultivation consists of controlling weeds, slugs and snails, and limiting the growth of the more vigorous plants which may tend to swamp smaller neighbours.
The average alpine plants with which a collection is started need no special winter care if they have been planted in suitable conditions as described above. If, during periods of excessive rainfall any which have very soft and hairy leaves seem to be suffering, they may be protected by a sheet of glass placed over them and held in position by easily contrived wire clips, but this is seldom necessary. The enemy of alpine plants is not cold, but wet. Most of them are accustomed to spend their resting period beneath a covering of snow.
- Alpine plants can be increased by various methods. The usual means of propagation are seeds or cuttings but old plants may often be divided, usually in early spring or early autumn, and a few plants may be increased by root cuttings.
- The seeds of alpine plants germinate more readily if they are sown as soon as convenient after ripening. If they cannot be sown at once they should be cleaned and dried and stored in a cool, dry place until sowing can take place.
- Sow the seeds in pans, pots or boxes, on a surface of finely sieved, rather gritty soil. Just cover the seeds with similar compost, stand the containers in a cold frame or greenhouse, or in a box out of doors and cover them with paper over which a sheet of glass is placed. As soon as they germinate they must be brought into the light.
- The seedlings are ready for pricking-off separately as soon as they make the first true leaves which differ from the first, or cotyledon leaves. John Innes seed compost is suitable, especially if a little extra fine grit is added.
- Cuttings of most alpine plants are made from soft tips of young growth which do not contain flower buds. They should be from 4-14 in. long. Trim off the lower leaves and, with a very sharp knife sever the cutting immediately below a node (leaf joint) and insert into pure gritty sand in pots or pans. Keep shaded and moist until the cuttings root, when they can be separately potted and grown on until well enough rooted to be planted out.
- Divisions should be potted and treated in the same way as potted cuttings. Make sure that all portions have some root. It is often possible to detach rooted pieces of old plants without digging up the entire plant.
Three Hundred Rock Plants Described
Acaena (Rosaceae) (New Zealand burr) Carpeting plants native, mostly, to New Zealand, these are invasive but ornamental and are useful for crevices of paving and to clothe areas of poor soil where little else will flourish. All are sun-lovers. Their small flowers are carried in dense heads on very short stems and are often accompanied by brightly coloured spines. They also make good ground-cover for dwarf bulbs. A. bttchananh has pea-green leaves and yellow-brown flower heads; A. glauca has silky, blue-grey foliage; A. microphylla has bronze leaves and innumerable scarlet burr-like flower heads.
Achillea (Compositae) (yarrow) Many of these sun-loving plants are suitable for the rock garden. They flower in spring and early summer and possess beauty both of leaf and flower. They are easily grown in any well-drained soil. The following are unlikely to exceed 6 in. when in flower. A. argentea has intensely silver leaves and white flowers; A. chrysocoma has grey leaves and yellow flowers; A. ‘King Edward’ has soft grey-green leaves and lemon yellow flowers, and A. tomentosa green leaves and bright yellow flowers. Aethionema (Cruciferae)(stonecress) Valuable dwarf, shrubby plants for places in full sun and any good garden soil, these flower from early summer onward. Propagate by seed or cuttings. A. grandiflorum makes a 9 in. bush of grey-green small leaves and has large heads of rose-pink flowers; A. pulchellum, similar but not so tall, has flowers the colour of pink coconut-ice. A. Warley Rose’ is a lovely, daphne-like shrub 6 in. tall with innumerable heads of rich rose-red flowers. As it is a sterile hybrid it has to be propagated by soft tip cuttings.
Alliurn (Lihaceae) This genus contains several fine rock garden plants; they mostly relish full sun and have no special soil requirements. A. karataviense, 9 in., has huge, handsome grey-green leaves and large ‘drum-stick’ heads of grey-white flowers in spring; A. moly, 9 in., is invasive but lovely. It has large heads of bright yellow flowers in spring; A. narcissiflorum has large, nodding wine-red flowers on 4-in. stems in spring. Alyssum (Cruciftrae) These easy-going, sun and lime-loving plants are very decorative in the early spring. They benefit from being cut back after flowering and can be increased from seeds and cuttings. They are splendid wall plants, especially when associated with arabis and aubrieta. They are mostly forms of A. saxatile, which has grey-green leaves and many heads of yellow flowers on 9-12 in. stems; `Compactum’ is dwarfer and more compact; `Citrinum’ has sulphur-yellow flowers, and ‘Dudley Neville’ orange-buff flowers.
A. spinosum (Ptilotrichum spinosum) though not strictly an alyssum is usually included in the family. It is a 9 in. tall spiny bush smothered with white or soft pink flowers in summer.
Anacyclus (Compositae) (Mount Atlas daisy) A. depressus makes prostrate mats of grey, ferny leaves and radiating stems carrying large daisy-shaped flowers, crimson on the back of the petals and white in front. It is a plant for full sun and very well-drained soil. Propagate from seeds.
Androsace (Primulaceae) (rock jasmine) This large genus contains some of the most desirable rock garden and alpine house plants. They are all sun-lovers and, as most of them have densely hairy leaves they may appreciate some protection against winter wet. Propagate by seeds or by detaching rooted rosettes or by cuttings. All are spring and early summer flowering. A. lanuginosa should be planted in crevices from which it can hang its trailing stems, which end in heads of pale pink, crimson-eyed flowers; A. primuloides (sarmentosa) `Chumbyi’, `Watkinsii’ and ‘Salmon’s Variety’ have neat, rounded, hairy-leaved rosettes and heads of deep pink flowers on 6-in. stems.
Anemone (Ranunculaceae) (windflower) Several species are admirable rock garden plants. They like well-drained, gritty soil, rich in humus and are increased by division or by seeds. All are sun lovers except where otherwise stated. A. ‘Lessen’, a sterile hybrid has glowing rose-red flowers on z ft. stems in spring; A. magellanica has creamy flowers in loose heads on 6-in, stems in spring and early summer; A. nemorosa, the wood anemone, likes partial shade and cool soil. The species has white flowers; the cultivars `Allenii’ and `Robinsoniana’ are blue. There is also a form with pretty, double white flowers; A. vernalis is one of the most beautiful of all alpines. It has huge opalescent flowers on 6-in. stems. It needs very gritty soil and sun.
Antennaria (Compositae) These easy little carpeting plants for sunny positions in any soil are invaluable for planting in crevices between paving stones. Propagate by division or seed. A. dioica has tiny grey leaves and fluffy heads of pink flowers on 3-in. stems in spring.
Aquilegia (Ranunculaceae) (columbine) Some of these are good rock garden plants. Few of them come entirely true from seed. They like sun and well-drained soil and flower in spring and early summer. A. ecalcarata has flights of elegant red-purple, spurless flowers on stems 9 in. tall. It comes true from seed; in A. flabellata, 9-12 in. tall, the large flowers may be blue or ivory-white; A. glandulosa has large blue and white flowers on 15-in. stems.
Arabis (Cruciferae) (rock cress) These sun and lime-loving spring flowering plants are easily grown in ordinary soil. Propagate by cuttings or seeds. Cut hard back after flowering. A. albida `Coccinea’ is the double white arabis, a valuable and showy spring flower; ‘Snowflake’ has large single, snow-white flowers; A. blepharophylla is very early flowering. It has pink blossoms on 6-in. stems.
Arenaria (Caryophyllaceae) (sandwort) These spring-flowering plants are easily grown. A. bakarica loves shade. It has a mere film of tiny leaves and clouds of dainty, tiny white flowers on 1-in. stems; A. montana is a spreading, sun-loving plant about 9 in. high, with innumerable large pure white flowers. Armeria (Plumbaginaceae) (thrift) These decorative sun lovers will grow in any soil. All flower in spring. Propagate by division or cuttings. A. caespitosa has tight tufts of closely packed deep green leaves and almost stemless heads of rich pink flowers; of A. maritima the best forms are ‘Vindictive’ deep red, `Laucheana’, crimson, and ‘Alba’, white. Asperula (Rubiaceae) These flower in spring and have clustered heads of pink or white flowers. Propagate by division, seeds and cuttings. A. gussonsi makes mats of dark green foliage and pink flowers. It will grow in any good soil; A. odorata, the woodruff, likes shade and cool soil. It has leafy 9-in. stems and heads of small white fragrant flowers; A. suberosa is an especially beautiful plant, but it needs gritty soil and a warm, sunny position. It produces soft carpets of grey leaves and clusters of tubular pink flowers. In wet areas it will appreciate shelter from winter rain.
Aster (Compositae) Those species suitable for rock gardens do well in open, sunny positions and in any good, well-drained soil. They may be increased by seeds or by division of old plants. Most flower in mid to late summer. A. alpinus has large blue and gold aster flowers on 9-in. stems. There is a nice white form and `Beechwood’ has large, more richly coloured flowers but is a little less ‘alpine’ in appearance; A. natalensis has flowers of gentian-blue on 6-in. stems. Astilbe (Saxiftagaceae) There are a few dwarf astilbes for cool, semi-shaded positions. Propagate by division of old plants. A. chinensis `Pumila’, 9-12 in., has stiff, dense spires of flowers the colour of crushed raspberries, in August and September; A. glaberrima `Saxosa’ has dainty spikes of pink flowers on very short stems in late summer.
Aubrieta (Cruciftrae)(rock cress) Aubrietas can be raised from seed and provide a mixture of colours. The best kinds are named and are propagated by cuttings or division. They are sun and lime-lovers and need to be heavily trimmed immediately after flowering to maintain their tidy habit and increase the length of their life. They flower in early spring. Any alpine plant catalogue will provide a list of names and colours, but the following may be regarded as a selection of the best kinds:
‘Bressingham Pink’, very large double flowers of rich pink; ‘Bressingham Red’, large flowers, deep glowing red; ‘Dream’, light mauve-blue; ‘Dr Mules’, one of the oldest and still a good one. Violet blue; `Godstone’, vivid violet-purple; `Gurgedyke’, deep rich purple; `Joan Allen’, double, deep red; ‘Mrs Rodewald’, very large bright red flowers; ‘Vanegata’, silver and green variegated foliage. Very compacrand neat.
Calamintha (Labiatae) These are pretty plants with aromatic foliage and worthwhile flowers, easily grown in any good soil and full sun. All flower in summer. Propagate from seeds or by cuttings. C. alpina bears violet, white-tipped tubular flowers on 4-in. stems; C. grandiflora is a slightly larger plant with border pink flowers. Ca in pan u la (Campanulaceae) (bellflower) Many campanulars are invaluable for the rock garden. Most flower in summer and late summer and are easily grown in good, well-drained soil and sunny positions. Those mentioned may be regarded as the essential nucleus of a collection. Propagate by seeds,. division or cuttings. C. carpatica has large, saucer-shaped flowers on 9-12 in. stems, its forms vary in colour from white to blue and rich purple; C. cochlearifolia (pusilla) is a tiny gem with blue or white bells on 3-in. stems; C. garganica is a splendid crevice and wall plant. The spreading stems cling closely to the stones and carry multitudes of blue, white-centred starry flowers; C. portenschlagiana (murahs), 6-9 in., is one of the very best. It has sheets of rich purple flowers in dense masses and will grow and flower in light shade; C. poscharskyana is semi-prostrate, invasive but very handsome and flowers for a long period. It has star-shaped blue flowers on long stems.
Cerastium (Caryophyllaceae) The common snow-in-summer, C. tomentosum is too invasive to be permitted in any rock garden although it is a decorative plant for wild places. There is at least one well-behaved, easily grown species however. This is C. alpinum `Lanatum’, which has dense pads of woolly grey leaves and small white flowers in summer. Grow in poor, gritty soil. Propagate by seed, division or cuttings.
Cheiranthus (Cruciferae) (wallflower) Wallflowers suitable for the rock garden like dry conditions, lime in the soil and a sunny place. Propagate by cuttings. C. cheiri `Harpur Crewe’ is the old double yellow Scotch wallflower with fragrant flowers in short spikes on stiff is-in. Bushes; C. ‘Moonlight’ is a deliciously fragrant dwarf plant with soft yellow flowers.
Chiastophyllum (Crassulaceae) In C. oppits:Whim (Cotyledon simphcifolia) the gol(len (lowers hang in slender chains from short leafy stems in spring. It likes a cool spot or light shade.
Chrysogonurn (Compositae) C. virgintanum is an easy plant for a not too hot place. It flowers the summer through. It has leafy stems and star-shaped yellow flowers. Propagate by division.
Cortusa (Primulaceae) C. matthiohi likes a cool position with moist soil. It has rounded lobed, softly hairy leaves and heads of pendent pink tubular flowers on 9-in. stems in summer. Propagate by seeds.
Cotula (Compositae) These are invasive but useful for paving and poor, stony soil. The flowers are inconspicuous but the foliage is pretty. They are invaluable ground-coverers. C. potentillina has deeply divided bronze-green leaves in dense prostrate mats; C. squalida has green, almost fern-like tiny leaves in close mats.
Crepis (Compositae) These showy easy plants for sunny positions in any good soil flower in summer. Propagate by seeds. C. aurea has leaves like those of a dandelion and copper-red flowers on 4-6 in. stems; in C. incana, 9 in., the leaves are ash-grey and it has showers of soft pink flowers.
Cyclamen (Primulaceae) The hardy cyclamen are invaluable tuberous-rooted plants for cool positions in the rock garden. Of the many cultivated species the three described are of outstanding virtue. They love lime but do not demand it. Plant them as growing tubers, not stored and dried ones which take a long time to grow. Plant 3-4 in. deep in soil rich in humus. Propagate by seeds. C. europaeum has marbled rounded leaves and pink fragrant flowers in summer; C. neapolitanum has beautifully shaped and marked leaves and deep pink-sometimes white-flowers in the autumn; C. repandum bears long-petalled rose-pink flowers in early spring. The dark green leaves are marbled with white.
Daphne(Thymeliaceae) This genus contains some of the most beautiful dwarf rock garden shrubs. They like sunny places but not dry conditions. The soil should be gritty and rich in peat or leafsoil. They are sometimes slow to establish but are long-lived. Propagate by cuttings and seeds. D. cneorum is a low bush smothered in summer with heads of rich pink, intensely fragrant flowers. If the stems become bare, fill up the plant with leafy soil; D. collina has red-purple fragrant flowers in spring and often again in late summer, on rounded r 5-in. Bushes; D. retusa makes a stiff, upright a-ft., bush with sweetly scented purple flowers followed by large red berries.
Dianthus (Caryophyllaceae) (pink) This is a large and valuable genus of easily grown, lime and sun-loving plants. Their colourful, often sweetly scented flowers are borne in summer. Propagate by division, cuttings, and seeds of those which are not hybrids. Many are fertile hybrids; seedlings of these will not come true but may produce some worth-while plants. D. alpinus makes low pads of dark green leaves and huge, almost stemless, rich pink flowers; D. arvernensis consists of ash-grey hummocks of leaves and 4-in. stems carrying rounded pink flowers. There is also a lovely white form; D. caesius, the Cheddar pink, has narrow grey leaves and large pink flowers on 6-9 in. stems; D. deltoides, the maiden pink, 9 in., makes sheets of flowers varying from light to dark pink; there is also a white form; D. ‘Pike’s Pink’ is very dwarf with large pink flowers over flat cushions of grey-green leaves; D. subacaulis forms green mats and has slender 4-in. stems carrying neat rose-red flowers.
Dodecatheon (Primulaceae) D. meadta likes a moist position or cool shade. It has pink and white, cyclamen-shaped flowers on 9-12 stems in spring.
Draba (Cruciferae) These spring-flowering plants are easily grown in sun and any good soil. Propagate by seeds. D. aizoides forms tufts of deep green pointed leaves and many yellow flowers in small clusters, on 3-in. stems; D. dedeana has grey-green leaves in huddled rosettes, and white flowers on r-in. stems.
Dryas (Rosaceae) D. octopetala is a woody plant with trailing stems and tiny dark green leaves. The large white flowers are abundantly produced in summer on short stems. Plant in full sun. Propagate by division or by cuttings.
Epilobiurn (Onagraceae) E. glabellum is a sun-loving plant which flowers from May until autumn. It has showers of large white flowers on branching, slightly arching 1 ft. high stems and bronze-green foliage. Propagate by cuttings.
Erigeron (Compositae) There are a few dwarf erigerons suitable for the rock garden. They are easily grown and like open, sunny positions. They flower in spring and summer. Propagate by seed or division. E. aurantiacus has rich orange flowers on 12 in. stems; E. compositus, 3 in. has tiny tufts of greyish leaves and soft lavender flowers; E.mucronatus (Vitadenis triloba) bears profusions of white, pale and deep pink flowers from spring until winter, on 9 in. stems. It likes dry, poor soil. Erinus (Scrophulariaceae) E. alpinus, 3 in., is an easy plant for sun or light shade, flowering in spring and delightful in rocky chinks. Propagate by sheds. It has soft pink flowers. There is a nice white form and several named forms of which ‘Dr Hanelle’, deep red, and ‘Mrs Charles Boyle’, rich pink, are the best. All naturalize freely but never objectionably.
Erodium (Geraniaceae) (heron’s bill) These important rock garden plants flower over a long summer period, are long-lived and easily grown in sunny positions, and any soil. Propagate by seeds or cuttings. E. chamaedrioides makes prostrate mats of dark green leaves studded with short-stemmed white, pink-veined flowers. The cultivar `Roseum’ has rich pink blossoms; E. chrysanthum has tufts of ferny, silver-grey leaves and sprays of sulphur-yellow flowers on 9-in. stems; E. corsicum has grey, hairy leaves in neat 4 in. high tufts and rich pink flowers. It loves a sunny crevice.
Euryops (Compositae) E. acraeus is a good dwarf silver-leaved bush of about 15 in., studded in summer with multitudes of golden, daisy-shaped flowers. It needs a hot, dry place. Propagate by cuttings.
Festuca (Gramineae) A few small alpine grasses are invaluable for filling chinks and crannies in the rock garden. Those described make neat, dwarf tufts, will grow in sun or shade and are propagated by division. F. glacialis, 3-4 in., has fine, grey-green leaves; F. glauca, 9 in., has ornamental silver-grey foliage; F. viridis, 4 in., has bright emerald-green leaves.
Frankenia (Frankeniaceae) F. laevis our native sea heath, is worthy of cultivation, but F. thymifolia, a better garden plant, forms prostrate mats of grey-green leaves and sheets of bright pink flowers in summer. It needs a sunny, but not dry position. Propagate by division or cuttings.
Genista (Leguminosae) (broom) These dwarf shrubs are essential in any rock garden. They relish open, sunny positions and dry soil. Propagate by seeds or cuttings. G. hispanica `Compacta’ is a spiky 1 ft. high bush covered in summer with golden flowers; G. lydia rather large for the rock garden, at 2 ft. high and 3 ft. in diameter, provides a sheet of rich yellow flowers; G. pilosa has prostrate woody stems covered with golden flowers in summer; G. sagittalis has curiously ‘winged’ stems which make low mats concealed in summer by yellow flowers.
Gentiana (Gentianaceae) (gentian) This is one of the most important genera of rock garden plants. They are too numerous to describe in detail and only a representative list of the most useful can be given. Their needs vary considerably and are suggested in the descriptions. Most of them are increased from seeds. G. acaulis is the ever-popular spring and summer flowering blue trumpet gentian. Plant very firmly in good loamy soil and sun; G. asclepiadea, the willow gentian, likes a cool position. Its 3-ft. Stems carry many pendent, tubular blue flowers in mid to late summer; G. septemfida, the ‘everyman’s’ gentian, will grow in almost any soil and open, sunny places. Sheets of blue flowers are borne in clustered heads on 9-in, stems in mid-summer; G. sino-ornata demands lime-free soil and a cool spot. It makes sheets of azure flowers from late August until winter; G. verna has clear blue star-shaped flowers on 3-in. stems in early spring. Grow in gritty soil, rich in humus, and full sun. Raise fresh seedlings every two or three years.
Geranium (Geraniaceae) (crane’s bill) Of this large genus several are admirable for the rock garden, in any good, well-drained soil and sunny positions. Propagate by division, seeds and cuttings. G. ‘Ballerina’, 6 in., has sprays of rounded pink flowers, veined with deeper colour the summer through; G. dalmaticum, has erect 4 in. stems which carry shapely pink flowers in summer. The foliage assumes rich autumn tints; Grenardii, 10 in., has lovely lobed leaves and pastel-lavender flowers; G. sanguineum `Lancastriense’ makes prostrate mats of deep green studded with large, saucer-shaped salmon-pink flowers; G. subcaulescens, 6 in., bears carmine, dark-eyed flowers all summer.
Geum (Rosaceae) (avens) At least one geum is an easily grown and showy alpine species, for full sun and any soil. Propagate by division or seed. G. montanum has large lobed leaves and huge golden, rounded flowers on 6-in, stems in summer.
Globularia (Globulariaceae) (globe daisy) These are sun-loving woody plants. Propagate by division, seeds and cuttings. G. cordifolia, a prostrate plant has tiny leathery dark green leaves and blue powder-puff heads of flowers on very short stems; G. trichosantha is larger in all its parts. It has quite large heads of blue flowers on 9-in. stems. Both flower in summer.
Gypsophila (Caryophyllaceae) (chalk plant) These easy and very showy plants trail effectively from walls and ledges. They are spring and early summer flowering. Propagate by cuttings. G. dubia has showers of clear pink flowers; G. fratensis bears rosy flowers in profusion; G. repens is best in the variety ‘Letchworth Rose’ which provides a mist of rich pink flowers on ft. high stems. Haberlea (Gesneriaceae) H. rhodopensis, 4 in., is a plant for cool, shady or north facing crevices. It has rosettes of deep green leaves and tubular lavender, gold-flecked flowers in spring.
Hebe (Scrophulariaceae) (veronica) This is the correct name for most of the evergreen shrubby plants often known as veronicas. It is a large genus and contains a number of valuable summer-flowering rock garden shrublets. They are easily grown in any good soil and sun, but some are slightly frost tender and should be placed in warm positions sheltered from early morning sun. Propagate by cuttings. H. ‘Carl Teschner’ is a 9-in, tall bush sheeted with purple-blue
flowers; H. macrantha, 18 in. tall is covered with very large pure white flowers. H. pinguifilia, 6 in., has grey leaves and myriads of small white flowers.
Heliantheminn (Cistaceae) (sun rose) For a summer-long display of brilliant flowers the sun roses are unequalled. They appreciate full sun and sharply drained soil and it is essential to trim them quite severely as soon as the flowers are finished. This not only keeps them in good and tidy health but usually provokes a second display of blossom in the late summer. Propagate by cuttings. There is a multitude of named varieties of H. nummularium: H. ‘Amy Baring’, 6 in. with orange-bronze flowers, is the dwarf of the race. Others range in height from 6 to 12 in.; H. ‘Ben Hope’, carmine flowers with an orange centre; H. ‘Broughty Beacon’, large flame-red flowers; H. `Croftianum’, silver foliage and apricot flowers; H. ‘Golden Queen’, rich yellow blossoms; H. `Henfield Brilliant’, glistening brick-red flowers, splendid new variety; H. ‘Jubilee’, double yellow flowers; H. ‘Mrs Earle’, double red flowers; H. ‘Red Orient’, glowing deep red flowers; H. ‘Snowball’, double .white flowers; H. Wisley Pink’, large soft clear pink flowers.
Helichrysum (Compositae)(everlasting, Immortelle) These are sun-loving plants, some shrubby, others compact tufts. They have attractive grey or silver foliage and showy flowers. Propagate by division, seeds or cuttings H. bellidioides forms grey mats of foliage and has white flowers in summer; H. frigidum has tiny silver tufts and daisy-shaped, golden-eyed white flowers in summer; H. milfordae has mats of glistening silver leaves and white, scarlet-backed flowers in spring and summer.
Hepatica (Ranunculaceae) These delightful early spring flowering plants do best in cool positions and light shade. They like soil rich in humus and can be increased by seeds or division of old plants, although old plants should only be lifted when really necessary as they resent disturbance. H. nobilis (triloba), 4 in., has dainty clear blue flowers; H. transsylvanica (angulosa) has larger leaves and larger flowers of equally vivid blue. Both are sometimes included in the genus Anemone. Hieracetun (Compositae) (hawkweed) This genus contains a few good rock garden plants. They are invasive and should be planted with this in mind. They do best in poor soil and full sun. Propagate by division or seeds. H. a urantiacum, 1 ft., has handsome heads of brilliant orange flowers in spring and summer; H. villosum, 1 ft., has lovely silver hairy leaves and yellow flowers from June to August.
Hippocrepis (Leguminosae) H. comosus ‘ER. Janes’ is a delightful creeping, sun-loving plant which covers its carpets of green leaves with countless lemon-yellow flowers in spring and early summer. Increase by division or cuttings. It flowers more freely in well-drained poor soil.
Houstonia (Rubiaceae) (bluetts) H. caerulea has myriads of small clear blue flowers on 3-in. stems in spring. It loves cool shade and moist soil and should be divided and replanted every two or three years.
Hutchinsia (Cruciferae) H. alpina is a pretty little plant for a position where it is shielded from full sun. Tufts of dark green leaves are enlivened by clouds of snow-white flowers on 3-in. stems in spring. Propagate by seeds.
Hypericum (Cuttiftrae) (St John’s Wort) These are semi-shrubby, summer-flowering, sun-loving plants. They flourish in any good well-drained soil. Their flowers provide brilliant colour and they are long-lived, especially if trimmed fairly severely after flowering. H. olympicum has brilliant golden flowers on 9-in. Bushes. There is a delightful form with lemon-yellow flowers; H. polyphyllum is a neat, 6-in, bush with bright green leaves covered beneath multitudes of rich yellow flowers; H. reptans is completely prostrate with trailing, leafy stems set with orange-yellow flowers; H. rhodopaeum, 9 in., has softly hairy grey-green leaves and soft yellow flowers.
Hypsela (Campanulaceae) H. longiflora is a prostrate plant, excellent for crannies between paving stones. It bears small lilac and white flowers in summer, likes a cool position and soil which does not parch. Increase by division.
Iberis (Cruciferae) (candytuft) These sun-loving, spring and summer flowering plants are easy to grow in any good soil. I. Gibraltarica has flat heads of white, lilac-tinted flowers on 9-in. stems; I. Jucunda, 6 in., bears large heads of white flowers turning to soft lilac as they age. It will flower until autumn – I. sempervirens ‘Snowflake’ is a spreading evergreen 9-in. Bushlet, smothered with snow-white flowers. It makes a magnificent display.
Iris (Iridaceae) There are various dwarf species and varieties which are invaluable rock garden plants for various positions. They are best increased by division after flowering. Unless otherwise stated all those described are sun lovers and do best in a lime-rich soil. I. Chamaeiris `Campbellii’ has large indigo-blue flowers on 4-in. stems in May-June; I. Innominata, 9 in. has stiff, narrow leaves in dense tufts and, in summer, flowers which may be golden, pencilled with chocolate, or a variety of pastel shades; I. pumila is grown in a variety of named forms, all usually less than 9 in. tall. The flower colour varies from white to all shades of blue and purple. It flowers in early summer; I. gracillipes likes shade and lime-free soil. It has dainty lilac and gold flowers on hi anching 6-in. stems; I. Cristata has lavender and gold flowers on 4-in. stems in late spring. It prefers a cool position.
Jasione (Campanulaceae) J. perennis is a pretty, blue-flowered plant but even better is Jjankae, which has large heads of clear blue flowers on 1-ft. Stems from mid to late summer. It is an easy plant for any soil or situation. Increase by seed or division of old plants.
Leontopodiurn (Compositae) L. alpinum 6-9 in., is the famous edelweiss. It will succeed in any good and well-drained soil and a sunny place. The tufts of narrow grey leaves are surmounted in summer by the characteristic heads of flowers which look as if they have been cut out of grey flannel. Propagation is by seeds.
Leucanthemurn (Composittie) L. osmarense, 9-12 in., is an alpine chrysanthemum of great merit. It requires a warm, sunny position in gritty but good soil, where it will make foaming masses of silver filigree foliage and carry innumerable large, white, golden-eyed daisy flowers throughout the summer. Increase by cuttings or seeds.
Lewisia (Portulacaceae) These are splendid spring and summer flowering rock garden plants. They prefer lime-free soil but will grow in alkaline soil if it is enriched with peat. They like sun and prefer to grow in crevices or on slopes rather than on the flat. Propagate by seeds and cuttings of side-rosettes. Keep plants dry after they finish flowering. They all have fleshy-leaved rosettes and when in flower vary from 9 to 15 in. in height. L. ‘Birch Hybrids’ range in colour from pink to deep salmon and crimson; in L. columblana `Rosea’ the wiry stems carry flights of red-purple flowers in abundance; L. ‘George Henley’ is a hybrid of great merit. It flowers from May until October with short, branching stems bedecked with brick-red blossoms; L. ‘Rose Splendour’ is another hybrid strain with very large flowers in which pale and deep pink predominate; L. tweedy,’ is perhaps the most splendid of the genus. It has lax rosettes of fleshy leaves and many large opalescent pink and salmon flowers carried singly on short stems.
Linnaea (Caprifoliaceae) L. borealis is the famous twin flower of the botanist (Carolus Linnaeus) whose name it commemorates. It is a woodland plant and creeps at sail level with wiry stems clad in tiny leathery leaves. The exquisite flowers, borne in spring, are clear pink bells carried two to each 1-in, high stem. It needs lime-free soil and shade or a north aspect. Increase by cuttings.
Linum (Linaceae) (flax) This genus contains dwarf shrubby plants and elegant perennials with tall stems and blue, yellow or white flowers. They all flower in summer and need sunny positions in good, perfectly drained soil. Propagate by cuttings or seeds. L. flavum is a stiff, 9-12 in. tall bush, with clouds of rich golden flowers; L. monogynum, 12-15 in., has large pure white flowers; L. narbonense bears huge funnel-shaped lovely flowers of gentian-blue on slender, arching 8-in. stems. L. salsaloides Nanum’ makes prostrate mats of tiny leaves on woody stems and large white flowers on very short stems.
Lithospermurn (Boraginaceae) The most widely grown and popular is L. diffusum and its forms. They are all lovers of hot, dry positions in full sun. They are propagated by cuttings. ‘Grace Ward’ has sprawling stems which carry myriads of vividly blue flowers throughout the summer. It makes a wide, semi-prostrate mat and must be given lime-free soil. With age the stems become bare, and then the plant should be liberally top-dressed with leafy soil.
Lotus (Leguminosae) L. corniculatus is our pretty native wildflower, lady-buckle-myshoe, which is too rampant a weed to be planted on the rock garden. The double form ‘Plena’, a desirable plant, makes a wide, flat mat, covered with golden flowers in the. Spring. It likes sun and sharp drainage and may be increased by cuttings.
Lychnis (Caryophyllaceae) (catchfly) Several species are excellent plants for the rock garden, easily grown in any good soil and sunny positions. Propagation is by division or seed. L. alpina is a tiny tuft of glossy leaves above which are carried, on 3-in. stems, clusters of small pink flowers early in the year. It is not long-lived and seeds should be sown every two or three years; L.flosjovis place. It makes 6-in, spiky bushes of sharp twigs and tiny grey leaves and carries many small pink flowers in summer. Propagate by seed or cuttings.
Maianthemuni (Lihaceae) M. bifolium is a shade-lover and grows best in lime-free soil. It is a pretty plant, 3-4 in. tall, a rare native, delightful in a cool corner of the rock garden. It creeps by underground stems and erupts into dense clusters of heart-shaped green leaves and fluffy heads of tiny white flowers in spring.
Margyricarpus (Rosaceae) M. setosus is a semi-prostrate shrub, 12-15 in. tall, its stems densely covered by small, pointed dark green leaves. The inconspicuous flowers are followed by myriads of round, translucent white berries. It grows in any good soil and sun, but should not have a parched position. Propagate by seeds or cuttings.
Mazus (Scrophulariaceae) These dwarf carpeting plants do best in cool rather than hot positions. They flower in mid to late summer and grow in ordinary garden soil. Propagate by division. M. pumilio makes green carpets studded with stemless blue and white flowers. It should be lifted, divided and replanted in fresh soil every so often; M. reptans has bronze-green leaves and flowers of mauve, white and gold. It is rampant and must be given room to spread.
Mimulus (Scrophulariaceae) (musk) These easily grown and showy plants like moist or cool position shaded from full sunlight. Several are invaluable for places by the sides of pools or streams. They flower in early summer and are increased by seeds, cuttings or division. Most are fairly short-lived and should be re-propagated every two or three years. M. burneth has red-brown, mottled flowers on 9-in. stems; cut down after flowering to produce a second blossoming the same year; in M. cupreus Whitecroft Scarlet’ the brilliant flowers are carried in abundance on 6-in. stems. Cut back after flowering; M. primuloides is a choice, tiny plant for a cool but not boggy position in the rock garden. It has gay yellow flowers on 2-in. stems. Divide and replant frequently; M. radicans likes a cool but not boggy position. It makes flat carpets of bronze leaves studded with stemless white and violet flowers all summer.
Minuartia (Caryophyllaceae) M. verna makes a delightfully neat little tuft of emerald green with gleaming white flowers on threadlike stems in spring.
Mentha (Labiatae) (mint) There are a few panion for Genttana verna, which dislikes mints which find a place among the alpines. Living in solitude. Grow it in full sun, in They flower in summer and are increased by gritty soil and propagate by seeds ,division or cutting. M. reguienii, the Corsican Nierembergia (Solanaceae) N. repens (makes a mere film of soft green which vularis) is entirely herbaceous and disappears spreads over the ground in moist or cool below ground in the winter. Its underground places and displays countless tiny, stemless creeping stems erupt in summer into bright lavender flowers. The whole plant is in- green leaves amidst which nestle large, white tensely peppermint-scented, stemless funnel-shaped flowers; it likes poor
Micromeria (Labiatae) All the plants in gritty soil and will flourish in a gravel path. His genus give forth a pungent but pleasant Propagate by division in spring.
Oenothera (Onagraceae) (evening primrose) M. coma likes a really hot, dry and sunny Several species are suitable for the rock has grey hairy leaves and large carmine-red flowers on 1-ft. Stems; They are all sun-lovers with no special soil preferences as long as it is well drained. They have a long flowering season from late spring onward and, although the flowers of many last for one day only, there is a constant succession to continue the display Propagate by seeds and cuttings. O. acaulis forms tufts of jagged-edged bright green leaves and has stemless clusters of white flowers which become pink as they age; A. fremontii, 9 in., has slender grey-green leaves and large bright yellow flowers; O. missouriensis, 9-12 in., a sprawling plant, provides an endless succession of enormous deep yellow flowers; O. pumila (perennis), makes small tufts of shining green leaves and bears neat, cup-shaped yellow flowers in profusion on 6-in, stems over a period of many weeks.
Omphalodes (Boraginaceae) These are very early flowering plants for light shade or a cool north aspect. They are not fussy about soil. Propagation is by division. O. cappadocica has fresh green leaves and showers of clear blue forget-me-not flowers on 9-in. stems in March-April; O. verna flowers earlier, is not quite so tall and the flowers are of a paler blue. There is a delightful white-flowered form.
Oxalis (Oxandaceae) Most of the species suitable for the rock garden are lovers of sun and warmth and good, well-drained soils. Propagation is by seeds or division. O. acetosella, the native wood sorrel, is one of the species which prefers a cool positron. The cultivated form aosea’ rambles about in light shade and woodland soil, producing many rich pink flowers on very short stems in spring and summer; O. adenophylla, 4 in., has deeply -cut silver leaves and countless funnel-shaped pink flowers in spring; O. enneaphylla produces grey leaves and large pink, Or sometimes white, cup-shaped flowers in spring. O. mops, 4 in., can be a weed, but it is a lovely one and should be spared a space where an invader is welcome. The
large beautiful rose-red flowers are produced abundantly in summer; O. lobata sends up, from tiny, hairy bulbs, in early spring, clusters of emerald-green leaves. These soon die down, to reappear in the autumn, accompanied by delicious golden flowers on 3-in. stems. It needs a warm corner and light soil; O. magellanica is a delightful plant for a cool position. Its minute dark green leaves make close mats and are studded with flat, pearl-white flowers in summer.
Papaver (Papaveraceae) (poppy) P. alpinum, the charming alpine poppy, is a short-lived plant but it perpetuates itself by means of self-sown seedlings in sunny places and light, gritty soil. The leaves appear in tiny tufts, surmounted throughout the summer by miniature poppy flowers which may be white, yellow, cream or shades of pink and red, on 4-in. stems.
Parochetus (Leguminosae) P. communisis a particularly lovely creeping plant which is hardy in a warm, moist position. The leaves are clover-like and the plant spreads by trailing stems and carries, during late summer and autumn, and often on into the winter, pea-shaped flowers of gentian-blue. Propagate by division or rooted runners.
Penstemon (Scrophulariaceae) These dwarf shrubs like warm positions and protection from east winds. A lime-free soil is preferable but not essential They flower from spring until mid-summer, Propagation is by cuttings of soft tips taken early in the year. P. davidsonn (rupicola), 4 in. has leathery grey-green leaves and ruby-red flowers; P. heterophyllus, 1-1 ½ ft., has spires of blue flowers; P. menziesii, 1 ft. has small, thick and fleshy, toothed leaves and violet-purple flowers; P. pinifolius 9-12 in., bears scarlet flowers in profusion; P. pukhellus is quite prostrate and bears blue flowers on 3-in. stems; P. roezhi; 9 in., makes a stiff bush covered with red flowers; P. ‘Weald Beacon’ is a lovely hybrid with glowing crimson flowers.
Phlox (Polemoniaceae) In this large genus there are many important rock garden plants. The species, selections and hybrids, loosely grouped as ‘cushion phloxes’ provide invaluable colour early in the year, are of neat habit, easily grown in any good, well-drained soil and benefit from being closely trimmed after they have flowered. Propagate by cuttings or division of old plants in spring or autumn. The most popular are the forms of P. subulata. All are sun-lovers and, although they will grow in light shade, they do not as a rule flower freely unless given full light. P. adsurgens is an exception in that it prefers a slightly shaded position. Its 3-4 in. mats are decorated by large, salmon-pink flowers – P. amoena has 6-in, stems which carry heads of purple flowers. There is a form with pretty, variegated foliage; P. divaricata is of rather loose, untidy habit but the large lilac flowers are carried in loose heads on 12-15-in. stems; the forms of P. douglasii are of close, cushion-forming habit and carry carpets of almost stemless flowers. Among the best are `Boothman’s Variety’, with clear mauve flowers, `Rosea’, rich pink, and ‘Snow Queen’, pure white; P. stoloniftra ‘Blue Ridge’, 12 in. is a lovely phlox with heads of clear blue flowers; P. subulata has several forms and it should be plentifully represented on every rock garden. They are also excellent plants for growing in walls, crazy paving, or for tumbling over a path-edge. They all make wide, low cushions covered with flowers: `Appleblossom’, soft pink; ‘Fairy’, small, neat flowers of lavender with deeper colour marking the base of the petals; ‘G. F. Wilson’, one of the oldest and still one of the best with mauve flowers; ‘Model’, rose-coloured flowers; ‘Pink Chintz’, clear soft pink blossoms; are excellent varieties. Phyteuma (Campanulaceae) Several species are worth growing in the rock garden in any good soil and an open position. Propagate by seeds. They flower in mid-summer. P. hemisphaericum has grassy leaves and heads of clear blue flowers on 6-in. stems; in P. nigrum the intense dark violet flowers are borne on 12-in. stems; P. scheuchzeri has rounded heads of deep purple-blue flowers on 12-in. stems.
Pimelia (Myrtaceae) P. coarctata is a completely prostrate woody shrub whose ground-hugging stems are clothed in tiny grey leaves. The plant is sheeted with small white flowers followed by translucent white berries. Propagate by cuttings or seeds. It needs very gritty soil and full sun.
Platycodon (Campanulaceae) (balloon bellflower) This handsome plant, valuable for mid-summer flowering, needs only full sun and any good soil. Propagate by seeds. P. grandiflorum `Mariesii’ is the most usually planted form. On 12-15-in. stems it carries huge, inflated buds which expand into rich-purple saucer-shaped flowers. The variety `Apoyana’, 6 in., is suitable for the small rock garden. There are also forms with white or soft pink flowers.
Polygala (Polygalaceae) (milkwort). P. calcarea loves chalky soil and sunny places. It has tiny tufts of slender stems and 3-in. Spikes of deep blue flowers in the spring; P. chamaebuxus likes a cool north aspect. It is a 6-in, evergreen shrub with clusters of cream and yellow tipped purple, fragrant flowers. Propagate by division in spring.
Polygonurn (Polygonaceae) (knotweed ) Two species at least are desirable: P. tenuicaule flowers in the very early spring, with short spikes of white flowers on 3-in. stems. Propagate by division; P. vaccinifelium is at its best from August until October. It forms dense mats of bronze-tinted green leaves on woody stems and has short spikes of heather-pink flowers. Propagate by cuttings.
Potentilla (Rosaceae) (cinquefoil) Some of these showy, easily grown sun-lovers should be on any well-planned rock garden. All flowers in spring and summer. Increase by seeds or division. P. alba is a sprawling plant, good for ground cover, with white flowers; P. aurea has sheets of golden flowers on prostrate mats of foliage. There is also a good form with double flowers; P. megalantha makes bold clumps of large, velvety leaves and huge golden flowers on 6-in. stems; P. nitida makes carpets of silvery foliage over which are set on very short stems pretty pink flowers. It needs very gritty soil; P. verna ‘Nana’, a prostrate plant continues to produce its golden flowers throughout the summer and well into the autumn.
Primula (Primulaceae) These are mostly spring and early summer flowering. Propagate by seeds or division. The latter operation yields the best results if carried out soon after flowering. Seeds should be sown soon after ripening. P. acaulis is the primrose, of which there are many double flowered and coloured forms, all good rock garden plants. They all like a cool position and deep, rich soil; P. auricula, 4 in., the alpine auricula, loves a sunny crevice from which to display its charming yellow, fragrant flowers; P. denticulata is a plant for a moist place. It has great heads of purple, crimson or white flowers on 1-ft stems; P. frondosa makes tufts of soft, meal-covered leaves and has rounded heads of pink flowers on 4-in. stems; P. minima, one of the smallest, has tufts of glossy leaves and large pink flowers on r-in. stems. It needs gritty soil; P. marginata, 6 in., is a fine crevice plant with white powdered leaves and heads of lavender flowers; P. rosea loves a really wet position such as a bog garden or by the edge of a stream. In early March it produces vivid carmine-red flowers on 6-9 in. stems.
Pulsatilla (Ranunculaceae) (pasque flower) The spring flowering P. vulgaris (syn. Anemone pulsatilla) loves full sun and chalky soil. There are many desirable forms, varying in colour from white through shades of purple to pink and deep red. The finely divided leaves make a handsome foil to the large flowers carried boldly on r-ft. Stems. Propagate by seed, sown as soon as it is ripe in late summer, in light soil in an unheated frame. Ramonda (Cesneriaceae) R. myconii demands a tight crevice between rocks with a cool, preferably north aspect. It has flat rosettes of leathery, wrinkled leaves and deep lavender, golden centred, flowers on 4-in. stems. Propagate by seeds or by very careful division.
Ranunculus (Ranunculaceae) (buttercup) Many species are valuable for the rock garden. They flower in spring and summer, thrive in sunny places and, in general are not at all fussy about the soil in which they grow as long as it is well drained. Propagate by seeds or division. P. amplexicaulis has large, flat-faced white flowers on 9-in. stems; R. ficaria, the lesser celandine is a pernicious weed but there are some good trustworthy cultivated forms, notably Aurantiacus’ which has coppery-orange flowers on 4-in. stems; R. gouanii has huge, saucer-shaped golden flowers on short stems; R. gramineus has narrow, grassy leaves and elegant, branching tz-in. stems carrying golden buttercups; R. montanus ‘Molten Gold’, a gem of a plant, very easily grown, makes low mounds of large golden flowers on very short stems, seldom more than 3-in. High.
Raoulia (Compositae) These are completely prostrate plants with minute leaves. They make good ground cover for tiny bulbs or for carpeting the soil beneath pygmy columnar conifers. Plant them in full sun. Increase by division. R. australis forms mats of intense silver leaves and has stemless golden flowers in the early summer; R. glabra makes green mats and has cream flower heads; R. lutescens is the tiniest of all, a mere film of grey-green which becomes golden with massed tiny flowers in early summer.
Salix (Salicaceae) (willow) Several delightful pygmy willows make entrancing little shrubs for the rock garden. They do not mind full sun, but like cool root conditions and will grow in light shade if necessary. They have fascinating gnarled woody stems and many of them bear pretty silver catkins in the spring. Propagate by cuttings. R. arbuscula a prostrate plant, has tangled woody stems and dark green foliage. It will spread over a considerable area; S. reticulata, another prostrate species, has lovely rounded leaves netted with conspicuous veins, and silver-grey catkins.
Saponaria (Caryophyllaceae) (soapwort) S. ocymoides is a useful and decorative plant to trail down from a high ledge or crevice. The long leafy stems carry, in spring, sheets of bright pink flowers. It is easily grown in sun or light shade and any soil. Propagate by cuttings.
Saxifraga (Saxifragaceae) (saxifrage) This is one of the largest and most important genera of rock garden plants. The number of species, hybrids and forms is legion and there are kinds for many different soils and situations. They vary from 1 in. to 1 ft. or more in height. Unless otherwise stated they like open, sunny positions and sharply gritty soil. According to their kind they can be increased by seeds, division and cuttings; each will suggest by its habit and appearance the appropriate method. Most of them flower in spring and early summer. Space permits mention of only a representative few of each of the many groups. S. aizoon is a large complex of slightly varying plants; the two most desirable varieties are `Lutea’ with soft yellow flowers and `Rosea’, soft pink. Both are about 6 in. tall; S. apiculata makes flat green cushions and has yellow flowers on 6-in. stems. There is also a good white form; S. burseriana is a choice plant of which there are many varieties. One of the best is ‘Gloria’ which has red stems and large white flowers on 3-in. stems over spiny cushions of grey leaves; S. cochlearis makes hard, humped cushions of congested grey rosettes and 9-in. Pink stems carrying white flowers in summer; S. fortunei has large lobed leaves, red on the reverse, and 18-in. stems carrying flights of white flowers in autumn; S. granulata ‘Plena’ is the double meadow saxifrage. It dies down in winter but bears massed double white flowers in spring on 9-in. stems; S. irvingii makes hummocks of minute grey-green rosettes and stemless pink flowers in great profusion; S. longifolia forms magnificent rosettes of symmetrical grey leaves and very long spikes of innumerable white flowers; S. oppositifalia flowers in very early spring. It makes prostrate carpets of dark foliage and bears stemless red flowers; S. urbium (umbrosa), London pride, is an old garden plant, still a deservedly popular favourite. It also has some attractive miniature forms.
The so-called ‘mossy’ saxifrages are a separate group. They like a little shade or a cool aspect. They all make compact mats and vary in height when in flower from 3-6 in. Such kinds as `Sanguinea Superba’, deep red; ‘Peter Pan’, pink; ‘Pearly King’, cream-white; ‘Winston Churchill’, deep pink and ‘Four Winds’ rich red, are all excellent. Sedum (Crassulaceae) (stone crop) Many of these easy, sun-loving plants are extremely decorative plants for the rock garden. Some species, of which S. acre and S. album are examples, are handsome but so weedy that they should be excluded from all but the wildest places. The few named below may be regarded as a nucleus of the best kinds. Propagate by division or cuttings. All are spring and early summer flowering unless otherwise stated. S. album ‘Coral Carpet’ makes flat mats of fleshy coral-pink leaves and soft pink flowers; S. cauticolum produces large heads of crimson red flowers on 6-in, trailing stems in late summer. S. lydium has tufts of small fleshy leaves, red in summer, green in winter. It bears white flowers in profusion, on 3-in. stems; S. spathulifolium has several good varieties of which the most decorative is Turpureum’, with purple fleshy leaves and golden flowers on 3-in. stems. In `Cappa Blanca’ the leaves are densely covered with white ‘meal’.
Sempervivum (Crassulaceae) (houseleek) These sun-lovers are best grown in poor, gritty soil. Very decorative and trouble-free, they carry quite good flowers but are valued most highly for the rosettes of fleshy leaves, often brightly coloured. Propagation is by division; few of them breed true from seed. One hundred or more species, forms and hybrids are available. S. arachnoideum is the cobweb houseleek – the green and red rosettes are spangled with tangled white ‘spiders-webs’ of fine threads; S. ‘Commander Hay’ has large deep red-purple leaf rosettes; S. tectorum, the common houseleek, is often seen in great clumps on cottage roofs. It is very variable and various forms are available. The species has green, purple-tipped leaves. Silene (Caryophyllaceae) (catchfly) These are easy plants for sunny positions, variable in colour of flower and ranging from high alpine cushion plants to tall border plants. Propagate by seeds or division. They flower in spring and summer. S. acaulis makes hard humps of tightly packed tiny rosettes and stemless pink flowers. It needs very gritty soil; S. schafta produces sheets of pink flowers on 6-in. stems.
Sisyrinchium (Iridaceae) These sun loving, summer flowering, plants have tufts of narrow, grass-like leaves. They are increased by seeds or division. S. brachypus, 6 in. has bright yellow flowers; S. angustifolium bears bright blue flowers on 6-in. stems.
Soldanella (Primulaceae) These lovely, typical alpine plants like cool positions and gritty soil, rich in humus. They flower in earliest spring. Propagate by seeds or by very careful division. Guard from slugs. S. alpina has tiny rounded, leathery, dark green leaves and fringed lavender bells on 3-in. stems; S. montana has larger leaves and wider flowers of purple-blue, on 4-6-in. stems.
Thymus (Labiatae) (thyme) These summer-flowering aromatic plants present no cultural problems in sun and well-drained Nod. T. citriodorus ‘Silver Queen’, a variety of the lemon thyme, makes an upright, 6-in. Bush of green and silver leaves; T. herbabarona is prostrate, its leaves strongly scented of caraway. It has pink flowers. T. drucei (serpyllum) has many named forms, all invaluable carpeters. Flower colour varies from white to deep crimson.
Tiarella (Saxifragaceae) T. cordifolia is a dainty, shade-loving spring and early summer flowering plant. It has elegant soft green leaves in neat tufts and fluffy spikes of white flowers on 9-in. stems. Increase by division. Veronica (Scrophulariaceae) This is a large genus varying from dwarf kinds for the rock garden to tall plants best suited to flower borders. They all love full sun and grow well in any good garden soil. Propagate by seeds, division or cuttings. All flower in spring and early summer. V. cinerea, 1 ft., has grey leaves and long spikes of blue flowers; V. prostrata, a low-growing plant, has several named forms providing low mounds of white, pink or blue flowers according to kind; V. teucrium ‘Royal Blue’ has deep blue flowers on t-ft. Tall stems. Viola (Violaceae) V. cornuta, the horned violet, bears graceful long-spurred lavender-mauve flowers on 6-in. stems. Grow from cuttings or seed. It grows in any good soil and sunny place; V. cucullata, 4 in. loves shade and carries large white, lilac-veined ‘violet’ flowers in spring. Increase by division every two or three years.
Zauschneria (Onagraceae) (Californian fuchsia) Z. califirnica, 9-12 in., is a plant for the hottest, driest available position, where it produces a riot of intense scarlet flowers over grey leaves in late summer and autumn. Increase by cuttings of soft tips.