Vegetables in containers and gardens : growing from seed (Best Gardening)

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Best Gardening

Growing from seed

Forget all those stories about seeds being hard to grow. Seeds are programmed to grow. The skills for growing seeds successfully are easily learned and equipment required need not be expensive. Sowing seeds is often thought of as a thing of the past. Punnets of pansies, lettuce and tomatoes are available easily and cheaply in the garden centres, why bother to sow your own? Well, quite apart from the satisfaction of watching seedling germinate and grow, sowing seeds saves money and makes a wider range of varieties available to the home gardener. Many heritage plants are only available as seed and it enables you to propagate more of your favourite perennials, annuals, vegetables and woody plants. Seed sowing is an all year activity, although spring is a time when we are busy planting both vegetables and flower seeds. In the colder months you can grow seeds indoors under cover ready for transplanting into the garden or for growing in tunnels or the greenhouse.

Sowing under cover
Sowing seeds into trays or pots for later transplanting into the garden extends your garden season by getting you off to an early start. You can grow plants that that need extra warmth to germinate or a long growing season.

Tender vegetables (e.g. lettuce) should be sown under cover in trays or pots so that they can be transplanted into the vegetable garden once the weather warms and the risk of frost is past. Runner beans and courgettes, marrows, cucumbers, tomatoes, lettuce, celery and leeks are amongst the many plants that you can start early under glass in this way. Petunias, snapdragons, cosmos and many other flowers can be sown indoors and transplanted into the garden.

Choosing Containers
Always use clean containers when planting. Last year’s seed trays and pots can be washed, to avoid the risk of disease, and reused. You can plant into seed trays or into individual pots. Some seeds, such as lettuce, are best sown in a seed tray, and then ‘pricked out’ after they have produced true leaves (not the first leaves) into seed trays, tubes or cells.

Other seeds, such as courgettes and beans, are best panted into an individual pot from the beginning, with the obvious benefit of less root disturbance on transplanting into the garden.

Alternatively, you can use plugs, planting cells or a similar, proprietary product from your local plant nursery. This is ‘cell-planting’ where a seed ‘tray’ is divided up into small cells, which minimise root disturbance when planting out.

You can make your own ‘cells’ with from milk cartons, cardboard strips or by rolling newspaper around a can or jar and flattening the bottom. Place in a seed tray and handle sparingly as these can be rather fragile. Newspaper cylinders can be planted intact but remove cardboard strips or milk cartons before planting, leaving the seedlings separated and easy to plant with minimal disturbance.

Seed Raising Soils
The soil mix you use is a matter of trial and error, and personal preference. Seeds need to be able to push new roots out into the soil to gain the nutrients and moisture they need. Seed starting soils ideally should be friable, absorb moisture but let excess moisture drain away, and not compact. Sterile soil reduces the risk of disease, and mixes with fresh compost and organic matter may not be suitable for this reason. There are many commercial mixes available for starting seeds, or a regular potting compost may be suitable. Homemade mixes can be very successful.

Sowing Seeds
Fill a container with seed mix and moisten (it should feel like a wrung-out dishcloth). Plastic pots and seed trays can benefit from a single layer of newspaper to prevent soil leaking, then fill your seed containers to the top of the lip and tamp the soil gently with the bottom of an identical pot. Toy blocks are often a perfect match for cell packs.

Sow seeds evenly in seed trays to encourage good growth. Crowded seeds will be leggy and compete for nutrients. Small seeds (lettuce and petunias) need to be planted less than a centimetre apart, medium seeds (tomatoes and marigolds) a centimetre apart and large seeds (peas) at least 2.5 centimetres apart.

In individual pots plant seeds towards the centre of each pot or cell. Plant two seeds per pot. This method is ideal for courgettes, marrow and plants with large seeds that need real warmth to germinate.

Cover the seeds according to the instructions – some seeds germinate better without light, others prefer it. The rough rule is to cover seeds to three times their diameter. Label the container, as it is very easy to muddle seedlings when juggling multiple sowings!

Where to grow undercover
A glasshouse, greenhouse, conservatory or bright (but not scorching) windowsill is ideal for starting seeds. Make sure that you turn the seedlings regularly to encourage even growth and prevent leggy seedlings.

Water gently and regularly to maintain moist but not wet soil. Lack of air circulation and over watering can lead to damping off, when the seeds collapse and die.

Pricking Out
When the true leaves have formed (the first pair of leaves that appear after the seedling or ‘cotyledon’ leaves) seedlings in seed trays are ready for pricking out. Prepare a new seed tray, cell pack or pot for the seedlings; poke a hole with a pencil or dibber into the soil. Taking a plant label, knife or pencil prise a block of seedlings from the seed tray. Using the sharp point carefully separate a seedling. Holding the seedling by a leaf (never the stem or roots) lower it into the hole in the new pot. Continue until all have been pricked out, water gently with a fine spray.

Larger seeds, such as marrow, courgette and sunflowers, can be planted two or three to a pot to ensure against seed failure. After germination, pull out the weaker plant and allow the remaining plant to grow on.

Hardening off
When seeds have germinated and been grown on undercover, the transplant shock into the big world of the garden is considerable. The climate is cooler, night temperatures are lower than in the protected greenhouse, and wind will lower temperature. To ease the transition seeds should be ‘hardened off’.

The ideal for this is to have a cold frame with a glass lid. By closing the lid overnight, the plants are protected from late frosts and cold temperature. The glass is gradually raised during the day until it is completely removed and the plants are then tough enough to make the transition to the garden. If you don’t have the luxury of a cold frame, take the seedlings outside for a longer and longer period each day.

Transplanting into the garden
When the seedlings have grown on they can be transplanted into the garden. Take the seedling out into the garden, which should be weed-free and worked up with the hoe to a fine tilth. Using your dibber make a hole in the new bed, and gently remove the seedlings from the pack, taking each plant at a time, plant to the same depth in the garden. Water in gently.

Do not transplant seedlings in the heat of the day, in bright sunshine or very drying, windy weather.

To protect newly transplanted seedlings or to get them started earlier than open planting you can cover the seedlings with a cloche. If you do not have a cloche then a soft drink bottle with the top cut off makes a fine individual cloche. Damp newspaper, weighted with earth, laid alongside new seedlings will help to retain soil moisture.

Sowing Direct in the Garden
Some vegetables and flowers are not suited to transplanting, for example most root crops, and should be sown directly into the garden.

Allow soil to warm before sowing seeds. Sowing seeds into cold, wet ground is a waste of time, they can rot and you may well have to re-sow later. Most vegetables need soil at 7o C before they will germinate. If sown earlier they will lie dormant, or rot and have to be re-sown.

If you have wet soil, you can sow other vegetables under glass and move them out when conditions improve. Or you can place a cloche over the soil for several days or until it has dried sufficiently, and then plant under the cloche. Always remember to check seeds planted under a cloche as they can quickly dry out.

Preparing soil for sowing
The ideal soil is moist but not wet or sticky, if it is compacted (i.e. flattened) when you walk on it, wait and sow later, or use a plank to distribute your weight.

If you must sow into cold ground you can cover the ground with black polythene or cloches, to raise the soil temperature and allow the soil to dry.

To prepare soil for seed sowing, first ensure that it is weed-free. Then break it up with a hoe and rake until a fine tilth. On dry or clay soils shuffle up and down, using your feet and the hoe to break up any clods, and then rake it. On very dry ground, water the soil sometime before you sow to allow the water to soak in.

Once you have achieved a nice, fine seed bed, use a line (length of heavy string drawn taut between two sticks) to draw out a shallow drill using the side of your hoe. The depth of the drill depends on the seeds you are sowing. If it is very wet and you must sow, add some fine sand to the base of the drill. Sow the seeds thinly in the drill.

Sowing the seed
With plants that need space to develop you can sow three to four seeds together at intervals, space the seeds at the eventual desired spacing for the plants. The seeds can later be thinned, but the seed that would have been sown in the intervening spaces has been saved. Try this with beetroot, cabbage, etc. You can sow a fast maturing crop, such as radish, between slower crops. The faster seeds will germinate and act as a marker for the slower crop, and can be harvested before it fills out.

With large seeds (peas, beans) place each seed individually at the correct spacing. Peas and French beans can be sown in drills 15-20cm wide, in effect getting two rows close together.

Mark the end of the rows with sticks and /or labels or you may loose track of where your new seeds have been planted. Cover the drill carefully with a rake and tamp down with the back of the rake. Water gently.

If you are sowing in blocks then cover the area with short rows or broadcast the seeds (i.e. scatter the seeds over the area & gently rake in). One way is to rake in one direction, sow the seeds and then rake again, at right angles.

When the seed has germinated and seedlings have developed true leaves you can begin to thin. Thinning seedlings prevents overcrowding allows good development of the remaining plants.

Thinning more than once will mean the some baby carrots or tender lettuce can be used in the kitchen. Check the seed packet for ideal spacing for maturing plants.

Succession Sowing
Don’t sow all the seeds in the pack, you’ll have far more flowers than most gardeners require or a sudden flush of lettuce or carrots and then weeks with none at all. Save some seed for next season (check the packet for viability dates) or do successive sowing to provide a long season of salad vegetables, carrots or late season sweet peas to pick.

Succession sowing is easy, just plant more seed every few weeks during the season to ensure a steady supply of salad greens, cabbage and carrots.

So get growing from seed
It’s fun and not all that hard, after all, seeds are programmed to grow!

Collecting seeds

Division, cuttings, ‘slips’. There are many ways to increase your stock of favourite perennial plants and to carry annual veges and flowers from season to season.

Collecting seed is one method often overlooked.

Some plants seed freely and widely. So much so that gardeners deadhead them quickly before they can takeover the gardens.

Other plants are worth collecting seed from. Wait until the seed heads or pods have dried, but not opened! Either cut them or shake them into a brown paper bag. Not a plastic bag as moisture is trapped, sweats and the seeds go mouldy. Label each bag as you go, it’s even harder to recognise seeds than plants!

Clean the seed by removing seed coverings, pods, petals and stems. Store in a cool dry place until ready to sow. Many seeds germinate better when fresh, hellebores often have prodigious numbers of offspring under their canopy as the seed has fallen and germinated fresh, but they are reluctant to germinate if even slightly stale.

Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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