Propagating Plants – Growing from seed

Growing from seed

propagating plants - growing seeds One great advantage of growing your own summer bedding plants is that you can pick and choose exactly what varieties you want, and can select individual colours rather than the usual mixed assortment that is available from garden centres.

Sowing half-hardy annuals

Sow the seeds in a pot or tray as described below, and leave it in a warm place. Keep a close eye on it, and wipe away surplus moisture from the pane of glass. From the moment the seeds germinate uncover the glass, as they will need good light as well as warmth.

As soon as the seedlings have their first pair of true leaves (in addition to their first ‘seedling leaves’) and are large enough to handle, prick them out into trays, spaced about 5cm (2in) apart, or in individual pots for larger plants such as Cobaea. Hold them only by the seedling leaves — if you squeeze this too hard the plant will recover, but once the stem is damaged, that is the end of the seedling.

Careful hardening off is essential, that is to say the seedlings have to be gradually weaned from the warm, draught-free conditions in which they have been raised until they are strong enough to withstand the more rigorous conditions outdoors. If hardening off is rushed, the seedlings may get a severe check in growth, which could set them back considerably, or even kill them. Their first change in temperature might be from a heated propagator to the greenhouse proper. After a week or so here to gain strength, they can be moved to the most well-ventilated part of the greenhouse, perhaps by the door. Another week, and they can be removed to a cold frame. More air may gradually be admitted to the frame until the seedlings only receive protection at night. Planting out can only take place when all danger of frost is past.

As you see, many half-hardy annuals need heat to germinate, followed by several weeks of warm, light, protected conditions. Then, during the slow process of hardening-off the young plants are still going to need warm nights. So, unless you have a heated greenhouse or conservatory, it is advisable to buy these plants.

Sowing Seeds

Unless you need a large quantity of plants, it is unnecessary to sow a whole seed tray – you can use a half-tray or a clean 8cm (3in) pot. Fill with a fresh seed compost gently so that it is within 1cm (1/2in) or less from the top. Scatter seed very thinly over the surface and sieve a little more compost on top using a fine-mesh sieve.

According to the temperature recommended on the seed packet, put the tray or pots either in the airing cupboard, on the kitchen window sill or in a propagator or greenhouse.

Herbaceous perennials

Many herbaceous perennials can be increased from seed. Most cultivars will not come true, but you may well end up with an interesting result. The method is the same as for half-hardy annuals, but instead of pricking them out into trays, they should be potted individually in 8cm (3in) pots, and may even need potting on again before they are large enough to be planted out in the border. They should be hardened off in the same manner as described above.

Obtaining rarer plants from seed

There is nothing more tantalizing than seeing a photograph of some desirable plant and not being able to get hold of it. There are numerous reasons why a plant is rare — it may be hard to propagate, or it may lack pot-appeal, in other words it looks unattractive in its pot at the garden centre. If it does not sell, nurserymen lose interest, the plant becomes scarcer, and the cycle continues. Or perhaps you live in some out of the way place where only a limited range of plants is available or you may find it hard to import plants. But there are rarely any restrictions on importing packets of seed through the post, and by growing plants from seed you will suddenly have access to a vast new range of trees, shrubs, herbaceous plants and alpines. You may need to join specialist societies and send off for their catalogues to see what is available as seed.

As regards the best time to sow, this is probably immediately the seed arrives. If the seed does not germinate in the first spring after sowing, it may well do so in the second. Try and find out what sort of climate the plant comes from in the wild. If you have seed of a plant you know little about, try sowing half the seed in warmth and the other half outside. Seeds from plants native to the temperate regions often need a period of freezing weather (as they would have had in the wild) in order to germinate. Some, such as peonies, can take a year or more to come up, and it is not until you are just about to throw the pot away that you notice the seedlings. By this time a soilless compost would have become compacted, so make a mixture of two parts soil-based seed compost and one part horticultural sand or sharp grit to assist drainage; since the pot will be outside in all weathers, it is important that it does not become waterlogged.

Use a clean 8cm (3in) pot. Fill it to within 1cm (1/2in) of the rim with the compost and firm gently with the base of another pot. Sow the seeds as thinly as possible — there is less danger of damaging the seedlings when transplanting if they are uncrowded. Sieve a very thin layer of soil over the top, about the depth of the seed itself, then put about 1cm (1/2in) of grit on top of the pot (unless the seed is very fine). This prevents liverworts and moss establishing themselves and conserves moisture. Water through a fine rose. Label the pot with the name of the plant and the date of sowing.

Place the pot in a shady place and water it now and again in hot weather. Success is not guaranteed, but you cannot imagine the joy of seeing a peony seedling appear, after waiting patiently for two years. If the seed germinates in early spring, and the weather is cold and wet, move the pot to a cool greenhouse or frame for protection. As soon as the seeds have their first true leaves, they may be potted individually.

27. December 2010 by admin
Categories: Propagation | Tags: , , | Comments Off on Propagating Plants – Growing from seed


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