Best Conditions for Sowing Seeds

Best Conditions for Sowing Seeds

Choosing composts

best conditions for sowing seeds Although it is easy to do, it is unlikely that you will want to mix your own sowing and potting compost — it would just never be as good as the best quality commercial brands (though it could not be poorer than the worst). Most composts are based on peat, sand and chemical fertilisers, while John Innes formula composts are based on sterilised soil, though they may still have some peat in them. Organic versions may duplicate these, or be based on composted or worm worked wastes. Sadly, in trials, many conventional and most peat-free and organic composts have proved inferior to the best peat-based or John Innes loam-based composts.

John Innes is a series of recipes for loam-based compost produced by different companies: John Innes No 1 is for sowing; No 2 for potting on; and No 3 for permanent pot plants or very hungry young plants such as tomatoes. If well made, John Innes is without doubt the best non-organic compost to use. Peat-based composts are as effective, if you don’t mind using peat products. There are now many peat-free composts on the market, but you may prefer to consider peat as a renewable resource we should be encouraging the sustained use of. Any sort of compost will deteriorate with age: never buy old, wet or end-of-season cheapies! Your safest bet is to buy a popular quality brand from a reputable supplier — or try several brands and see which suits what you grow the most. It is most interesting to sow the same seed in three or four different brands in a mini-trial at home!

For sowing, use a freshly sieved seed or multi-purpose compost, John Innes No 1, or a home-made mixture — either peat and sharp sand, or sieved sterilised garden soil, peat and sharp sand. For rooting cuttings, use a mixture by volume of any sterile sowing compost with sharp sand. For small, tender and valuable seedlings pot up into a reputable brand of potting compost, such as John Innes No 2 — stronger and bigger plants may prefer the richer No 3.

For robustly growing plants, pot them up into either a fresh organic compost or sieved garden compost. I use the latter for almost all my potting, making it extra strong for hungry feeders such as courgettes, melons and cucumbers by thoroughly mixing in grass clippings.

Light, temperature and water control for sowing seedlings and young plants

Although the very best plants are usually grown where they are sown, many accidents can happen on the way. A dedicated seed bed improves their chances and the hardier seedlings grow away well. But often even with cloches a sowing may be unsure in cold soil or the germination may inconveniently be expected to take years. Seed is usually easier to germinate in warmth under cover, and success is more certain with plants started in little pots or multi-celled trays and planted out when they and the site are ready. Indeed, some long-season and tender plants, such as tomatoes must be started this way, otherwise they would never have time to crop in our short growing season. However, although ensuring survival, transplanting almost always checks the plant’s growth and it rarely does as well as it might have done sown in situ. We must minimise such checks, and with pots we must take more care as we affect their conditions more than in the soil.

Almost all crops that are best started off in pots benefit from being started in multi-celled trays, because these give each plant its own little space with minimal root interference. The insulated trays are easy to fit in a propagator and move around in pots or cells. Never risk letting seedlings crowd each other. The commonest mistake is sowing thickly in one pot, intending to prick out later, and leaving this operation a day or two too long, which causes severe losses of yield.

A few annual and bedding flowers, beetroot and onions can be allowed to have two or three seedlings growing together to produce clumps of smaller plants. For other plants, sow two or three seeds in each cell or pot and thin as soon as possible after they emerge.

When sowing in pots or cells, extra care needs to be taken with watering, so as not to waterlog the seeds; nor allow them to dry out. It is best to fill pots with damp compost, then stand them in a tray of water till the top looks wet. Remove and drain well. Do not re-water until the seedlings appear unless the compost starts to dry out badly. Never use stale rainwater for seeds or seedlings as this can spread damping off disease. For valuable seeds even bottled water is not too great an expense, but tap water will usually do. Once the plants are growing strongly then rainwater is preferable, because it contains no added chlorine, fluoride, etc.

A greenhouse is not needed for starting off hardy plants in cells or pots, because they will be more than happy in a coldframe or a sheltered spot until they are ready to go out. However, a greenhouse allows you to control conditions more easily and can later be used for growing tender crops to fruition. Cloches are nearly as good, but do not have as much space and are difficult to use. A polytunnel gives the best value for money, though they are not very nice to look at. Whatever you choose, be careful to keep the glass or plastic clean as light is more important than heat for most plants, especially hardy vegetables. Ventilation is also important, since it is easy to cook small seedlings if full sun hits them while they are tightly sealed up, so either be extra vigilant or invest in an automatic vent opener.

Once hardy plants have started growing well in pots they can be planted out into the main plot. However, they must be hardened off. This simply means getting them used to the tougher conditions by standing them outside during the day and bringing them back under cover at night for three or four days. Do not skimp on this — it is most important. If you have to plant out partially hardened off plants, protect them after planting with cloches or clear plastic bottles. If the weather is poor or the plot is not ready for planting out when the plants are big enough, they must be potted on into larger containers or they will stop growing. When planting out hardened off or seedbed-grown seedlings, water them well the day before and, if possible, prepare the planting holes and water them too. Certainly water the holes long enough before planting to allow the water, with a dash of seaweed solution, to percolate away. Do not plant in mud! Make the holes bigger than the rootball of the plant, but not too deep. For the hungry feeders — including brassicas, sweet corn, tomatoes and cucumbers — mix a handful of sieved garden compost in with the soil before you replace it firmly around the rootball. As most seedling transplants are succulent, protect them from bird damage.

Growing tender plants from seed is more difficult, because most of them require starting off in warmth early in the year when light levels are low and they easily get leggy. They also need repotting several times as they cannot be planted out even under cover before summer unless you give them extra heat. In fact, the biggest problem is not germinating them, as any little propagator on a sunny windowsill will do that but where to keep them in the warm while they get bigger and bigger in larger and larger pots. Heating the greenhouse is an excellent if expensive option, but I suggest constructing a heated coldframe in an unheated greenhouse – it’s cheaper, and the same place is useful later in the year for luxury crops such as melons.

03. January 2011 by admin
Categories: Propagation | Tags: , | Comments Off on Best Conditions for Sowing Seeds


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