Charlbury Garden Society

Growing your own plant from seed in the spring

By Peter Bridgman

Raising your own plants from seed is, in general, the least expensive way of getting new plants for your garden, window sill or conservatory but there are several things you need to know

1. What do you want to grow and where should you buy your seeds?

Garden centres are the obvious choice but you could get a wider range by sending for catalogues and buying seeds online. The choice can be overwhelming. Some firms like Chiltern Seeds carry a very large range of types and varieties whilst others concentrate on a few specialist lines.

2. Price

There is a saying that “good seed is never expensive”. And certainly some seed varieties especially F1 hybrids are expensive to produce and therefore to buy.

However, if you want every plant to look like the picture on the packet you may need especially bred “F1 hybrids”. These are seeds sourced only from the best types, grown in isolation to avoid crossing with inferior types. They are more expensive but should produce good results.

3. Sowing medium – Compost etc.

Compost for seed sowing needs to be low in nutrients (food), reasonably fine and well drained. For most purposes I find multi-purpose compost (for example B & Q Verve Multipurpose with added Vermiculite, about 30%) works well.

Note that Vermiculite in compost is better than Perlite for germination. This is because Vermiculite extracts food making the compost less rich, and moisture. It holds the moisture for longer.

Note also that John Innes compost is a recipe not a brand – seed recipe is 2 parts loam, 1 part peat, 1 part sharp sand or grit – ideally all lime free. Peat free compost is good but you should ensure the texture is not too coarse. It must retain moisture and be low in nutrients.

4. Sowing conditions

Some hardy plants can be sown direct out of doors such as hardy annuals like cornflowers, pot marigolds, alyssum etc. whilst many others will need to be sown in pots or trays under cover.

For most domestic use, trays are too large for sowing seeds from the packet so a pot will give you sufficient space. You will often only use part of a seed packet in any one year so save the seed left over in its packet, ensuring the seed is dry, put it in a small tin and store the tin in the freezer.

Rather than use a round plant pot try using square pots that fit 15 to a seed tray. Then as seeds germinate at different speeds you can extract the square pot when it is ready to prick out.

Seedlings will need to be pricked off into individual trays or pots and grown on with protection, possibly extra heat and certainly adequate light to avoid “drawing”, the term often used for when plants grow tall and leggy.

For larger seedlings, however, such as courgettes, runner beans, broad beans, French beans, sow singly in deep plastic pots which could be 5 inches long. A common brand name is Rootrainers. They may be planted out directly from the seed pots and may not need to be pricked out.

Note that some seeds, for example lettuce seeds, need cool germination conditions. In fact, when growing for succession, growers sometimes have germination trouble with the later sowings in summer because it is too warm for the seeds to germinate.

5. Covering seeds after sowing

Containers should be filled to the brim with the compost and then firmed down gently with a level surface.

You will need to water before sowing but don’t flood the seeds.

You may also need to water after sowing but before germination. If watering is necessary use a fine rose or a spray.

As a rule sow seeds to a depth of about three times the seed’s size so bury large seeds deeper and sow fine seed very thinly. For example lobelia seeds are very small and if you sow too heavily they will develop into clumps or damp-off due to being too close together.

Remember that seeds will refuse to germinate if sown too deeply.

Some seeds need light to germinate – the seed packet should tell you so they should not be covered but will still need protection from direct sunshine. Read the packet carefully, it will give more precise information.

Vermiculite makes a good cover for seeds that need to be covered.

Tomatoes for example must be covered otherwise the seed may germinate with the seed coat intact preventing the seed leaves from developing,

After sowing cover the pot with plastic or glass.

Then place the pots etc. on a windowsill preferably facing north where there is shade. Direct sunshine or a greenhouse will often be too hot.

6. Pricking off

Always handle seedlings carefully keeping the roots intact and hold the plant by a seed leaf (the first leaf showing), never the stem. Make a hole with a pencil or dibber deep enough to take the root without bending it back. Gently firm and then settle the soil down with a light water.

Frequently asked questions

  • Can I keep seed for another year?

Generally yes but some seeds like primulas and delphiniums have a short viable life but can still be kept in small tins in the freezer. All seeds will live longer if deep frozen but quite a few will survive for a few years in a dry cool place. But see the comments above on F1 hybrid seeds.

  • How do I tell if seeds are still good?

If possible sprinkle a few on some kitchen paper – moisten and cover with plastic and keep in a warm place. If they germinate within a week or two all should be well.

  • Can I trust purchased seed to always be good?

No. There is no way to tell whether dry seed in a packet is good or not. You just have to trust the seedsman. If you sow seed within the time stated on the packet, in good conditions and it fails to grow, you could demand a replacement or your money back but you will have lost a whole year’s growing season. Always buy seed from a Garden Centre or Nursery who keep their seed indoors and away from the sun.

So, finally, have a go. Those little seeds are a treasure trove of joy.