Diarmuid Gavin's guide to growing from seed
Published 13/03/2016 | 02:30
Nothing is more rewarding in gardening than the feeling of propagating plants from seed - and I'm delighted to say that you are now perfectly in time to start this year.
Don't be scared, most are incredibly simple to germinate. What they need is some warming soil, a little bit of water, and to be given their own patch, and within days or weeks they will appear - two tiny leaves at the end of a short stem pushing up out of the compost. From these small beginnings you can have the basis of an amazing garden.
So what do you need to get started? For best results, use special seed compost - this has the correct texture and nutrient level for seeds. You'll need seed trays or modular pots which make transplanting easier. You can also use recycled yoghurt pots or even old egg trays will work.
For seeds that need warmth to boost germination, a heated greenhouse is perfect, but you can also use a small heated propagator or even a sunny windowsill. Once seedlings emerge, light is important but you don't want to scorch the tender shoots either.
If you're a novice gardener, start off with hardy annuals which complete their life cycle of growth, flowering and setting seed in one year, as these are the easiest to propagate. These can be planted indoors now or straight into the ground if it is sufficiently warm. How do you know if that's the case? Soil needs to be about 6˚C for germination (or just stick your finger and see if it feels warm). Sow too early and seeds may fail to germinate or rot. So, if you live high up a mountain or are in a frost pocket, or your ground is waterlogged, wait until conditions improve. You can still start them off indoors in readiness for when the soil warms up. You can also help heavy clay soil heat up by covering it in plastic or with cloches. Polytunnels will also extend your growing season.
When sowing outdoors, prepare your seedbed so it is clear of stones and weeds and rake to a fine tilth. Half-hardy annuals can't go out until after the last frost or they will be destroyed, so these you start off indoors and transplant around the end of April. These flowers come from more exotic climates and they generally like heat to get going (around 18-21˚C) so this is where a heated propagator is invaluable.
Fill containers with compost to within about an inch of the rim, firm down gently and water the compost. Now sow your seeds according to instructions on the packet - they will give you correct depth and space. In general you try to sow as thinly as possible; with larger seeds, say around three to five seeds in a pot. Overcrowded seeds won't do well and are more prone to fungal diseases. Some seeds, such as lobelia and petunia, are as fine as dust so it's a good idea to mix these with a bit of silver sand for more even distribution. When they are that fine, don't cover them with more soil. For most other seeds, sieve some compost gently over the top or a light drizzling of vermiculite which is excellent at keeping moisture in.
Don't forget to label as you go along. After an initial watering, cover with polythene or piece of glass to retain moisture until the seedlings emerge, then remove to avoid excess humidity which encourages fungal diseases. Now you wait until the first sign of green - this usually is in a few weeks. As soon as they have two sets of leaves you can prick them out of the trays and plant into pots using a wooden skewer (known as a dibber). Hold the seedling by a lower leaf, not the stem which will bruise easily.
All plants raised inside should be gradually hardened off before being transplanted outdoors. Start them off with a couple of hours outdoors, for example on a sheltered porch.
And what about growing veg from seed? The same principles apply. Some veg are hardy and can go straight into the ground while others are tender and need to be started off indoors. Sow the following under cover over the next month: aubergine, French beans, beetroot, broccoli, cabbage, cauliflower, celery, courgettes, cucumbers, peppers and chillies and tomatoes. From April you can sow directly in to the ground broad beans, calabrese broccoli, carrots, leeks, lettuce, onions, parsnips, peas, radishes and spinach. Quick-maturing vegetables, such as carrots, French beans, peas, and salads can be sown successionally - this just means sowing fresh batches every fortnight so you are getting a continuous steady supply rather than one big glut.
The best way to learn about seeds is through trial and error. You'll get a great sense of achievement when it works!
When watering seeds, use a rose on your watering can to ensure a light spray that won't disturb the seeds. Don't let your pots and seed trays dry out but be careful not to over-water and drown them either.