To raise plants from seed is not only a saving of expense, and an interesting hobby, it is also the best way to get strong plants that will make a permanent home in the garden. Everyone who has tried this method and compared it with the method of buying seedlings, discovers how much better the quickly transplanted seedlings from the home seed bed take to their flowering quarters than do the seedlings that come from a distance.
There is, of course, another side to the picture. Except for hardy annuals,. the raising of seeds entails some extra labour, and generally a good deal of extra space, either in the open, or under glass, or both. In the case of perennials, too, there may be some difficulty over variety. Many of the best of our border flowers are sports, i.e. variations of an older and less spectacular flower. Some are seedlings of mixed parentage: the seedlings raised from their seed will not necessarily come true to the type of the plant that produced the seed. In fact, to raise perennials from seed nearly always involves some degree of uncertainty, but there is always, as Compensation, the glorious uncertainty of possibly finding a new, outstandingly good flower among your batch of seedlings.
However, let us look at this question in detail, and perhaps we shall find that the difficulties and work of seed raising are not so great as we imagined. .
ANNUALS IN THE OPEN
Take the easiest kind of sowing first, the kind that most children understand. That is, sowing hardy annuals in spring, in the open garden. All that is needed here is a patch of well dug soil, not necessarily very rich, but not too poor, and preferably in full sunshine. The surface should be raked to a level, stone-free condition.
Annual seeds vary in size. The larger ones, such as Lupins, can be laid out singly on the soil, in the place where the plant is wanted. A group of seven seeds, each about 5 in. from its neighbour, would make a nice display in a mixed border. When the seeds have been spaced out, push each one down into the soft earth, so that when the surface is patted down flat again the seed will have twice its own depth of soil over it: say about I in. to 1 in. of soil. If the seeds are very small, as are Shirley Poppies, they can be sown thinly in lines, parallel to the front of the border, or can be broadcast over a prepared patch of soil. The difficulty here is to sow thinly enough: mixing the seed first with some silver sand is a help, and also shows clearly where the seed has fallen. In addition, the light surface of sand makes it unnecessary to cover the seeds, as they soon wash down with rain into the tiny crevices of the soil.
Annual seeds germinate very quickly, especially if sown during a warm spell. They almost always come up too thick and some of the seedlings must be removed to allow the others to grow to full size. It is best to thin out in successive stages, but as soon as the seed leaves are fully developed, some of the unwanted seedlings can be nipped off at soil level; this should leave one seedling every inch or two. As more leaves develop, more thinning must be done to leave the plants the room they will need, when mature. Use a little discretion here. In poor soils the plants are not likely to become exhibition size, and may be allowed a little less space per plant than on richer soil. For border edgings, dwarf crowded plants may be preferable to isolated large specimens. Flax and Virginian stock are examples of edging annuals that need not be thinned out at all if they are sown sparingly.
Some hardy annuals need stakes, but well-grown plants, not crowded, and grown in good soil, are less likely to need stakes than starved weakly specimens. The lighter annuals, with thin stems and foliage, need only a few twigs set among the seedlings when they are about 4 in. high. Heavier annuals may need several stakes set round a group, with garden string or raffia passing from stake to stake. The outer plants of each group should be tied individually to the outside of the stakes, so that the supports are practically invisible when the flowers are in bloom.
HARDY BIENNIALS AND PERENNIALS
Biennials, the plants that do not reach maturity until the second season after sowing, but, like annuals, are grown for a single season of bloom and then scrapped, are usually not sown in the border where they are to flower, but are grown first in a nursery bed. Wallflowers are a typical example. These can be sown in lines, drawn with a pointed stick, in the surface of well dug and well raked soil. A little lime in the seed bed is welcome, and if there is any doubt about the food supply, a light dressing of balanced fertilizer can be given to the soil before the final raking. Draw the lines for the seeds about an inch deep and 8 in. apart. This will allow for the use of the hoe between the rows, to destroy weeds.
Sow thinly: if seeds are costly, sow each one separately if possible so that no thinning of the tiny seedlings is needed. When the plants are an inch or two high (or larger, if they were sown very sparingly), it may be as well to move them to a fresh position, where they can make good plants. Wallflowers sown in April or May might perhaps be moved, as small plants, to the late potato patch, the plants being set at the bottom of the ridges made in earthing up the potato crop. Here they will remain until the lifting of the potatoes in autumn, when the wallflowers will be ready to set out in formal beds or borders, among spring bulbs.
Perennials, the border flowers that grow on from year to year, are raised from seed exactly as are the biennials, the only difference being that the perennials should, as soon as possible, be set out 3 in. to 6 in. apart in the row (according to kind) in a nursery plot, as soon as they can be handled. It is possible, with many annuals, biennials, and perennials, to thin out and waste the surplus seedlings, or to transplant each one and so avoid waste. With annuals, transplanting is not always a wise proceeding, as the move gives the plant a check, from which it has no time to recover. When raising perennials, however, transplanting should always be the rule, and no seedlings should he wasted. The reason for this is that perennial seedlings are likely to differ in colour and form (unless a fixed strain of seed can be bought), and very often the seedlings that appear to be weakest turn out to have the finest colours or forms of flower. Some perennials flower in the same season as sown : some take several years to reach flowering stage. (Irises, and some of the lilies take a long time!) To stock a new garden, however, it is well worth while to raise a good many hardy perennials from seed. It is cheaper, and because some of the plants may turn out to be extra fine, it pays to raise a quantity, and when they have reached flowering stage to go over them very carefully and take out those of inferior quality. The remainder can then be propagated by other means: division, cuttings and so on.
RAISING HALF-HARDY PLANTS
Some annuals, biennials, and perennials are not hardy enough to be sown in open ground. In addition, the raiser often finds that it pays to sow very early in the season, when open air sowing would be impossible. Another reason for sowing indoors is that some seeds are very rare and expensive, and greater care can be given theria under glass than in the garden, where birds and other pests can attack them.
The method of sowing under glass is the same for all kinds of plants. A pan or box of special seed sowing compost is advisable. The John Innes Research Station has experimented for many years, and has finally announced that the best seed sowing compost for general use is prepared by mixing good loam (sterilized), peat (or sterilized leafmould). and sand, with a little superphosphate and chalk, in the following proportions: 2 parts loam, 1 part peat (or sterilized leafmould). 1 part coarse sand, with 11 oz. Superphosphate and oz. Chalk added to each bushel of the
mixture. This appears to be the ideal for almost every kind of seed raised by amateur gardeners. This seed raising compost can be purchased from any sundriesman, and it is worth its cost to any raiser of good seeds.
The box or pan should allow for drainage: sides and base of boxes generally fit badly enough for this: and pans should have crocks set dome-wise over each drainage hole. The seed compost should at first loosely fill the container: slight even pressure will then bring it down to half an inch or so below the rim, so that watering is easy. A special pressing tool can be made by nailing a small thick piece of wood on to a piece of board. The edge of this board can serve another purpose: to make indented lines on the soil surface, into which seeds can be dropped at regular intervals. A scattering of soil to cover the seeds completes the task of sowing.
Most seeds germinate better in the dark than in the light. A sheet of brown paper and a sheet of glass over each box will make for rapid germination, but the paper should be removed immediately the seedlings are visible. From this time on, the young plants should be allowed the maximum of light possible. Without sufficient daylight, they will become weak and drawn, and will never make strong adult plants.
The question of what temperature to give seed pans and boxes is generally a matter of knowing the plants, but most seed packets or catalogues announce this for the benefit of beginners. It is not wise to keep the temperature up more than-is necessary. Plants become too tender and unable to stand up against weather vagaries when they reach the garden.
The time of sowing must also depend as much on particular conditions of each garden and greenhouse as on the type of plant. Half-hardy annuals are sown in February, March and April under glass, but it is useless to sow so many pans or boxes in February that they need more under-glass accommodation than can be given, for the plants will reach a good size long before the frosts are past.
A cold frame or two, in addition to a greenhouse, makes possible much more seed raising than just the greenhouse alone. As the plants become large enough to be pricked off separately into small pots, or into other boxes, they can be gradually hardened, that is, after a day or two to establish their roots in the new box or pot, they can be moved to the frame, where extra night protection will be given in the event of late spring frosts. The frame lights can later be left off entirely except on cold nights, and eventually the pots or boxes can stand for a few days in the open, before they are set out in borders.
With seedlings on the move in this way, a succession of sowings can be made, beginning with the hardier types of flowers first: antirrhinums, or alyssum, for instance: and waiting until later to sow ornamental gourds and other plants that will need a lot of room very quickly, but cannot stand even a few degrees of frost.
A reminder is needed here to those who own small glasshouses. These could be beautified very much by growing from seed in them a few of the ornamental annual climbers: the Cambridge-blue Ipomaea rubrocoerulea, variegated Cobaea scandens, with mauve flowers, or orange, buff, salmon or coral Thunbergia. Trained to wires or sticks, these need not occupy a vast amount of floor or staging space, yet they redeem the appearance of the greenhouse both from inside and outside.
The following lists should help those who wish to raise ordinary popular garden plants from seed. They cannot be entirely comprehensive, as practically every known family of flowering plants could be raised from seed in a greenhouse, if temperature and atmospheric conditions are adjustable. These are, however, the amateurs’ friends, easy to propagate and to grow on in ordinary greenhouse and garden conditions.
ANNUALS TO SOW DIRECT IN BORDERS
*Alyssum maritimum *Limnanthes Douglasii (”Eggs *Calliopsis and Bacon”)
Calendula officinalis (Marigold) Linaria maroccana Centaurea cyanus (Cornflower) *Linum (Flax) Clarkia elegans Lupinus (Lupin)
Collinsia *Malcomia (Virginian Stock)
Delphinium (Larkspur) *Matthiola bicornis (Night- scented Stock)
Eschschol tzi a (Californian *Nemophila (Californian Bell- Poppy) flower)
Gaillardia picta Nigella (Love-in-a-Mist)
Godetia Papaver (Poppies)
Gypsophila elegans *Reseda (Mignonette)
Helianthus (Sunflower) Salvia (Clary)
*Iberis (Candytuft) *Silene pendula compacta
Lathyrus odoratus (Sweet Pea) *Tropaeoleum (Nasturtium and Lavatera Canary Creeper)
Dwarf types of these families are suitable for border edging.
BIENNIALS TO SOW IN THE NURSERY BED
Anchusa capensis Lunaria (Honesty)
Antirrhinum Matthiola (Stocks)
Campanula (Canterbury Bell) Myosotis (Forget-me-nots) Cheiranthus (Wallflowers)
Coreopsis glandiflora Oenothera (Evening Primrose) Dianthus barbatus (Sweet Wil- Papaver nudicaule (Iceland liam) Poppy)
Digitalis (Foxglove) Verbascum (Mullein)
N.B. Some of these are perennials, but do best with treatment as biennials.
(to be raised under glass)
Amarantus (Love lies bleeding) Brachycome •
Callistephus (China Aster) Celosia (Prince of Wales Feather) Dianthus
Dimorphotheca (Star of the Veldt)
Helichrysum (Everlastings) Heliotropium (Cherry Pie) Helipterum Impatiens (Balsam) Ipomaea
Kochia (Burning Bush)
N.B. Many of these can be sown in the open, late in the spring, in warm gardens.
PERENNIALS EASILY IN THE OPEN (Likely to produce good seedlings if a good strain of seed is purchased.)
Achillea Aconiturn Alstromeria
Anthemis Aquilegia Aubretia Auricula
Bellis perennis (Double Daisies) Campanula
Catananche Centaurea Chrysanthemum
Dianthus (Pinks and Carna-
PLANTS TO RAISE UNDER GLASS
(Preferably in the cool greenhouse)
These include all the half-hardy annuals in the list previously given, and also : Antirrhinums Begonias Gazania
Cinerarias Japanese Chrysanthemums Meconopsis Dahlias Ricinus