Rules for Sowing Seeds

Rules for Sowing Seeds

The techniques of cultivation are much the same for all kinds. All seeds require warmth, moisture and air for germination which means that the soil in which they are sown must be crumbly so that water and air can penetrate freely, and moderately firm so that roots of seedlings make easy contact with it. If seeds are sown under glass or in other protected places it will almost certainly be most convenient to have them in pots, pans or seed trays filled with growing mixtures specially prepared for the purpose (gardeners rather confusingly call them ‘composts’ , a term they also use for decaying organic matter, a very different material).

These mixtures may contain soil, the basic formulae usually being based on those devised at the John Innes Horticultural Institution in the 1930s and known as John Innes (JI) seed and potting compost. Or they may be ‘soilless‘ or ‘peat’ types, and consist of peat, usually with sand or vermiculite added. All these composts can be prepared at home or purchased ready-mixed for use.

rules for sowing seeds Outdoors, you must usually make do with the existing soil on the site, but this can often be improved out of recognition by digging, forking, raking and mixing in peat, coarse sand, old mushroom compost, decayed garden refuse or anything else that will open up the soil, making it more crumbly and therefore more like the special seed composts used under glass.

Lime is also an excellent improver of the texture of sticky clay soils but it has one drawback for gardens, namely that a good many ornamental plants thrive best in soils that are slightly acid or neutral and lime tends to make soil alkaline. This is less of a hazard for annuals than it is for shrubs and other perennials, for most annuals are fairly soil tolerant, at least as far as an acid/alkaline reaction is concerned. All the same it is best to be sparing with lime.

You can begin sowing some half-hardy annuals in heated greenhouses as early as January, but late February is a better time in home gardens because by then it is easier to maintain the necessary temperatures. The days are getting longer and the light more intense, factors which make it easier to keep seedlings growing sturdily. Sowing can be held back even later, but then flowering will be delayed. Outdoors it is rarely safe to sow annuals until mid-March and then only if the soil can be worked easily and is not sodden and lumpy. In many places mid-April sowings made in good soil and weather conditions can be more satisfactory than March sowings; the plants, because they have never been checked, may be sturdier and start to flower just as early.

All seeds should be sown thinly since overcrowded seedlings quickly become weak and are much more likely to be attacked by disease. In pots, pans, seed trays or other containers, seeds are usually scattered evenly all over the surface, a method known as ‘broadcasting’. Some of the larger seeds can be spaced out singly about 1/2cm (1/4 in) apart. The soil in the container should be perfectly level, moderately firm (a couple of sharp raps on a firm bench will settle it down nicely and can be followed by a good watering from a can fitted with a fine rose) and reach to about 1cm (1/2in) below the rim of the container. The seeds are covered with a sprinkling of the same mixture, just sufficient to keep them out of sight but not to bury them to any depth. The compost can then be watered again, once more using a fine rose to prevent disturbance of the surface, then each container can be covered with a sheet of glass laid on top to keep in the moisture.

When all the containers have been sown and covered in this way, a single thickness of newspaper can be laid over them to shade the seeds until they have germinated. It must be removed directly seedlings start appearing, and a day or so later the sheets of glass can be tilted a little, then after another day or so removed altogether. From this time onwards, most seedlings will require all the light that is going. Only a few exceptional kinds will need any shade so early in the year.

Outdoors annuals may be sown broadcast, which is convenient if they are to be grown in patches of one kind, or in ‘drills’, the tiny furrows made with a pointed stick or the corner of a hoe or rake. The advantage of sowing in drills is that the seedlings of the garden plants will all appear in rows, whereas weed seedlings will be distributed at random and will be easier to spot and remove.

For most seeds the drills need be no more than 1 cm (½ in) deep and they are refilled, after sowing, by drawing the displaced soil back into them. Seeds are sown just a little more deeply out of doors than under cover since they need protection from disturbance by wind and heavy rain.


Planting Out the Seedlings

Seedlings grown in containers must be transplanted after a few days before they become weakened by overcrowding. ‘Pricking-out’, as this is termed, is about the trickiest part of the whole operation as the tiny seedlings are fragile and easily damaged. They can either be tipped out very carefully or lifted, a few at a time, with a sharpened stick (a wooden plant label will do). They are then separated and replanted 4-6cm (1-½ – 2-¼in) apart in seed trays filled with the same’ type of compost as that used for germination. The same sharpened stick can be used to make little holes for them but the forefinger is quicker and even more efficient.

Seedlings raised under cover must be acclimatized to outdoor conditions before they are finally planted out. The most efficient way to do this is to move them into a frame for the last fortnight, for this can be left completely open by day if the weather is favourable and partly open at night if there is no threat of frost.

Outdoors, seedlings will need to be thinned out and many kinds can be transplanted elsewhere if they are dug up carefully with a little soil adhering to their roots. Transplanting is most successful on a damp day after rain but if there is none, the seedlings should be well watered a few hours in advance.

All that has been said about the cultivation of half-hardy annuals applies equally to tender annuals up to and including pricking-out, but slightly higher temperatures may be required for some. Pot on the seedlings singly, this time into a rather richer potting compost. They are then grown on under cover with no hardening-off or planting-out. Make sure that the final pot is large enough to cope with the fully grown plant. Biennials germinate one year but do not flower and produce seed until the next year. Monocarpic plants, which include many species of meconopsis and also Saxifraga longifolia, take an unspecified time to complete their cycle. Some actually live for a number of years before they flower but once they do their end is near.

Although biennials have a regular life extending over at least part of two years, it is necessary to raise them anew from seed every year if flowers are to be enjoyed every year. Just as with annuals, there are numerous plants that, though not truly biennial, are conveniently treated as such since they produce the best and most reliable results when grown in this way.

Seed of most biennials and monocarpic plants (also of most true herbaceous perennials) is best sown in May or June. Usually by then it will germinate quite well outdoors but it may be easier to care for some of the rarer, more expensive or more difficult seeds if they are sown in pots, pans or other containers and germinated in an unheated frame or greenhouse.


05. April 2011 by admin
Categories: Garden Management, Propagating Plants | Tags: , , | Comments Off on Rules for Sowing Seeds


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