Growing Healthy Plants From Seeds

Seeds provide the cheapest way of producing many plants and the only way of producing annuals and biennials. Some seeds are very easy to grow; others are more difficult and there are a few that give trouble even to experienced gardeners.

Three things are necessary for the germination of all seeds: warmth, moisture and air, but they are necessary, particularly the first two, in varying degree according to the nature of the seeds. Those of very hardy plants, such as chickweed and groundsel, two of the commonest annual weeds in the garden, will commence to grow at temperatures around 7 C. (45 F.) whereas seeds of tomato will not start to germinate below I3°C. (55°F.) and those of the Indian shot plant, or canna. May need as much as 21 ‘C. (70°F.) to stir them into growth. Again. Seeds ofcacti will grow readily in soil that is only just moist, whereas seeds of the common run of non-succulent plants grow faster and more reliably in a moderately moist soil, and aquatics require a very wet soil, maybe one actually submerged in water. However, just as there are basic rules for planting, so there are basic rules for sowing, and to avoid repetition I shall deal with these here, leaving exceptions to be described under the particular plants.

Preparations Outdoors

Seeds of hardy plants, such as hardy annuals. Hardy herbaceous perennials and most vegetables, can be sown out of doors. The most favourable times are in spring, late summer and early autumn. During the winter the soil is likely to be too cold and wet for germination, and if the seeds lie around dormant for months, many of them may be eaten by birds, slugs, insects, etc., or may rot.’ In summer the soil tends to be too hot and dry, but these are faults that can be more readily overcome by watering and shading.

Soil in which seed is to be sown should be crumbly and reasonably fine. Small seedlings cannot push their way past big clods of compacted soil. To get this crumbly condition it is necessary to cultivate the soil well so that surplus water can run away and air can penetrate to dry the clods. Frost also helps, for the expanding ice pushes the particles of soil apart and when the thaw comes they crumble. This is the reason for the frequently repeated advice to dig seed beds in the autumn and leave them rough throughout the winter so that a considerable surface of soil is exposed to frost.

Final Soil Preparation

Whatever the preliminary preparation may be, the final preparation must be done shortly before the seed is to be sown and when the physical condition of the soil is right. This means that it must be moist below and. If possible, dry or drying out, on top. When the clods are struck with a rake or fork they should fall apart into crumbs, and it should be easy with these tools to break the whole surface down to a fine, crumbly, level seed bed. Sometimes it is necessary to watch quite closely for the right moment to do this. It is much easier to prepare good seed beds on sandy soils than on those containing a lot of clay and it may even be necessary to mix sand and peat with the clay to get a seed bed suitable for some of the more difficult seeds.

Under Glass

Under glass things are much more under control. A mixture of soil can be prepared that has exactly the right qualities, or substitutes for soil can be prepared.

John Innes Seed Compost

What is known as the John Innes Seed Compost is used by many gardeners and can either be prepared at home or purchased ready mixed. The basic ingredients, by volume, are 2 parts medium loam, 1 part peat and 1 part sand. The loam should be of good quality, without free lime but not too acid (/;H 6-5 is ideal) and neither too heavy nor too light. Before use it should be sterilized, preferably by steam, at a temperature of 93 C. (200 F.) for 20 minutes. The peat should be fibrous or granular and reasonably free from dust. The sand must be very coarse and sharp. Ranging in particle size up to Jin (025 cm). All ingredients must be mixed thoroughly. And to every bushel of this mixture should be added I^oz (40 g) superphosphate of lime and ^ oz (21 g) of finely ground chalk or limestone. These are required to rectify certain chemical changes caused by the sterilization. This mixture, and others containing sterilized loam, can be stored for a time but tends to deteriorate with age.

Soilless Composts

An alternative to soil mixtures are those based on peat, either by itself with suitable fertilizers, or with sand, vermiculite etc., but without soil. In a simple mixture of half moss peat and half coarse sand or horticultural grade vermiculite. Most seeds will germinate well, but as this contains little plant food the seedlings should be moved fairly quickly to mixtures containing either soil or fertilizers or be fed with liquid fertilizer.

Soil Moisture and Temperature Requirements

Under glass the seed compost (as the mixture is called) can be made just as moist as is ideal. Usually this should be sufficiently moist to allow the compost to bind into a ball when squeezed in the palm of the hand. But sufficiently dry to permit this ball to break up into small fragments when tossed lightly back on to the heap.

Under glass, too, the temperature can be adjusted to suit the seeds being sown. A good average to aim for is 16 to i8°C. (60 to 65°F.), in which most seeds will germinate well.

Preparing the Containers Under glass seeds may be sown in pots, pans or shallow boxes usually known as ‘trays” or ‘flats*. Whatever is used there must be holes or slits in the bottom for drainage, and, except in the case of plastic pots and trays, it is a good plan to cover these with some broken pieces of flowerpot, known as ‘crocks’, or with specially shaped pieces of perforated zinc to prevent fine soil washing down into the holes and blocking them up. The containers. Of whatever nature, should be not quite filled with soil, which should be made firm with the fingers and then made quite level by pressing with a smooth, flat piece of wood, usually referred to as a ‘patter’. Little or no firming is needed with peat and sand, peat and vermiculite or pure peat composts which should simply be settled in by rapping the container smartly on a solid surface such as the potting bench.

Seed Sowing

Seeds can be sown broadcast, in drills or singly. Broadcasting is mainly used for hardy annuals sown outdoors where they are to flower and for seeds sown in pots, pans or boxes under glass. The seeds are simply scattered very thinly all over the particular area where they are to grow, and then some sifted soil is scattered over them, or outdoors the soil is gently raked to stir the seeds in, just as when sowing grass seed to make lawns.

Sowing in drills is used for most vegetables and also for seeds of ornamental plants when sown outdoors with the object of transplanting the seedlings later. This is necessary with most biennials and perennials. The method is to stretch a line, or place a rod to serve as a straight edge and then, using this as a guide, to draw a little furrow with a pointed stick or the corner of a hoe. The seeds are then scattered thinly in this furrow, or drill, and the displaced soil is raked or pushed back over them.

The advantage of sowing in drills is that, when the seedlings germinate, it is much easier to see them and to distinguish them from weeds because they are in straight rows, and it is also easier to stir the soil between them with a stick or hoe to kill weeds.

Sowing singly is practised outdoors with big seeds such as peas, beans and sweet corn, which can be dropped one at a time into a drill or into little holes made with a stick. Under glass it is sometimes used for valuable seeds or to save time in pricking out, as the seedlings will be evenly spaced and have room to grow on undisturbed for several weeks. But the time so saved is usually more than lost in the rather fiddling task of spacing out the seeds.

Pelleting seed, i.e. coating each seed with smooth paste which dries to form a little ‘pill’, makes it much easier to space seeds singly. Pelleted seeds can be purchased but cost more than untreated seeds.


Watering and other Attentions Outdoors there is little to be done until the seeds appear, unless the soil becomes very dry, when it should be watered from a sprinkler. Or with a watering-can fitted with a rose. Under glass more watering may be necessary, though if each seed box, pan or pot is covered with a sheet of glass or polythene film, water will not evaporate very rapidly. Some seeds germinate better in the dark and so, when sown under glass, are covered with newspaper, but if this is done the news-paper must be removed directly the seedlings appear or they will be greatly weakened. Sheets of glass should also be tilted up a little a day or so after the first signs of germination, and removed altogether a day or so later. Most seedlings need plenty of light and air, and become thin and pale and tend to decay if deprived of them.

Thinning out Seedlings

Out of doors seedlings are usually thinned where they grow, which simply means that where they come up crowded some are carefully pulled out to leave the rest sensibly spaced.

Pricking out Seedlings

Under Glass Under glass the seedlings are ‘pricked out”, a term used for transplanting a seedling. They are lifted very carefully with a pointed stick or anything else convenient, are separated out

singly and then replanted in other boxes, pans or pots, for which purpose a pointed stick or dibber is generally used. With this holes are made about I \ to 2 in (4 to 5 cm) apart, the seedling is carefully held by a leaf between finger and thumb, its roots are dropped into the hole and the soil is pressed around them with the stick. Later on it may be necessary to transplant the seedlings again, and then it is usually done singly into small pots. Sometimes pots made of compressed peat or sawdust are used, and then, if the seedlings are to go outdoors later on, pot and all can be planted as it will gradually rot away in the soil.

For pricking out, the same compost as that used for seed sowing may be used, except that ‘if it is a peat/sand, peat/ vermiculite, or pure peat mixture, a little compound fertilizer should be added. Proprietary peat-based seed composts have the right kind and quantity ready mixed in.

Hardening off Seedlings All seedlings raised under glass must be hardened off before they are placed outdoors. This means that they must be gradually accustomed to the very different conditions they are going to face. First the greenhouse can be allowed to get cooler, or the seedlings can be moved to the coolest part of the house. Then, a week or so later, they can be removed to a frame where they should be given increasing ventilation, or to a very sheltered place outdoors. Only when they have become thoroughly accustomed to full exposure should they be planted out.

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