Sowing Seed

Sowing Seed:

Starting vegetables under glass, in a greenhouse or on a windowsill, can give a head start on the growing season, allowing you to make early progress while conditions outside are still unsuitable for growth. The techniques are simple and the equipment basic : all you need are fresh or carefully stored seeds , a supply of good compost, and containers large enough to accommodate about six weeks root growth until the young plants are picked out prior to transfer to the open ground.

Compared with sowing and growing outdoors , however, raising plants indoors is an artificial process, the success of which depends on providing perfect conditions during the critical weeks between sowing the dormant seeds and moving the transplant into the garden or allotment. Although all seeds are naturally primed to grow and survive in the right environment they face various hazards on the way, and when grown under glass their welfare is entirely in your hands.

Compost:

The perfect growing medium for indoor sowing needs to be moisture-retentive; well aerated and fine enough to make good contact with the seeds; and free from pests and diseases . It should also be low in nutrients , not just because all seeds contain a store of food sufficient to sustain growth until the seedlings’ own leaves can manufacture their own, but because an excessive amount can actually harm them during the first weeks of life.

Make sure you choose a compost specifically intended for seed-sowing. This will be finer than a potting compost, ensuring good contact all round the seeds to help them absorb moisture, and low in nutrients, which helps avoid the risks of over-feeding in the delicate early stages. The composts may be soil based, as with John Innes types, or soil-less, made from peat or a peat substitute with small amounts of slow-release foods adequate for about six weeks growth. Make sure it is fresh- never save last year's compost.

Both kinds of compost perform well but need slightly different treatments. Soil-based mixes should be gently firmed in the container to ensure no air pockets remain and so guarantee an unbroken flow of moisture throughout. Soil-less mixes are better settled in place by sharply tapping the filled container a few times on the bench , then very lightly pressing down all round the edges. If you firm them down to hard the mixtures tend to become airless and difficult to re-wet if they dry out. Never sieve seed compost too finely as this can result in a dusty surface that hardens into a crust, excluding air and impeding growth.

Germination:

Every seed contains an embryo plant that remains safe and dormant as long as the seed is dry. Absorbing moisture (imbibition) is the first stage of germination, and once started cannot be reversed without damaging the embryo. As well as a continuous supply of sufficient moisture, germinating seeds need oxygen , so the soil or compost in which they are sown must drain easily without waterlogging. And they need sufficient warmth to support steady development.

The minimum heat threshold vegetable seeds need for rapid emergence can vary widely from around 5 degrees for peas, broad beans and most brassicas to as much as 15 degrees for peppers and aubergines. Some seeds may still germinate at lower temperatures , but more slowly and erratically, while some are sensitive to too much heat : the onion family, for example, resents anything much above 21 degrees and lettuces (except iceberg varieties) are note for failure to germinate when summer temperatures exceed 25 degrees. Follow the recommendations on the seed packets carefully or, as a rough guide, aim for somewhere in the range of 10-15 degrees.

Herbs like sweet cicely and many nuts and fruit seeds need exposure to a minimum amounts of cold to break their dormancy, because they are adapted to surviving harsh winter conditions before germinating in the spring warmth. The traditional practice is to stand pots of these seeds outdoors over winter, protecting against mice with netting. Alternatively they are soaked overnight to soften the seed coat, mixed with moist sand in plastic bags, and then refrigerated for two to three months before sowing in the usual way.

Common Causes of Germination Failure:

No one knows how many seeds die before emerging outdoors-whether deliberately sown or spread by the wind. Under cover failure is more obvious and often results from neglect, accident or oversight during those hazardous first few weeks of plant life. Some of the more common problems include :-

OLD SEEDS -Always use new seeds or first test a sample of stored seed.

STALE COMPOST- Use a fresh supply and discard old stocks at the years end.

DRY COMPOST- Make sure it is moist, and water well before and after sowing.

RICH COMPOST -Use the correct seed mixture, which should be low in nutrients.

SEEDS SOWN TOO DEEPLY- Cover seeds with compost no deeper than twice their diameter.

LACK OF AIR- Avoid over-firming and over watering compost.

LACK OF SHADE-Hot sunshine can dry compost and scorch emerging seedlings.

WRONG TEMPERATURE-Check say temperatures are not too high or nights too cold.

Damping Off Disease:

One more vital factor influencing germination is freedom from disease, which is why bought composts are always sterilised. The main threat comes from soil-dwelling fungi that kill seedlings before they appear or cause them to collapse and die after they do. Cold, wet or poorly ventilated conditions favour what is known as damping off disease, as do dirty containers or labels and rainwater that has stood too long in water butts. The problem manifests itself most commonly in greenhouses. Always aim for sterile conditions when sowing indoors, create the most favourable environment for fast germination , and use clean water for irrigation. Nowadays seeds are to expensive to lose.

Picking Out:

Seedlings that have been sown en masse will need transferring to containers filled with nutritious compost before they are very large. Failure to give seedlings more room to develop quickly leads to deterioration as they fight for light and space. Pick them out as soon as you can easily handle them individually by their seed leaves. Don’t touch bulbous plants like onions until the looped single seed leaf begins to straighten up. Never hold seedlings by their stems, which are fragile and easily damaged. Tap the containers on a bench once or twice to help loosen the seedling then use a dibber to ease out the seedling. Settle the seedling in your larger container using the dibber to make a hole, then gently firm the seedling in place. Label and water with a fine rose on the end of your watering can. Keep the seedlings at a lower temperature than during germination to avoid forcing soft unhealthy growth, and in good light (but away from direct sunshine for the first few days, as they may scorch).