There are few things in life so satisfying as growing plants from seed. Most of us started with cress, sunflowers, radishes and beans when we were children. Whether or not we produced the tallest sunflower or longest bean pod, a genuine sense of achievement was gained through the knowledge that we’d assisted nature in producing new life. The good news is that if you can grow these easy pleasers from seed, there are tens of thousands of other plants that are equally as simple and rewarding to sow.
Ranging in size from specks barely visible to the eye to giants the size of a coconut, seeds are one the main ways that plants reproduce and multiply. Some are trickier to coax into life than others, but the majority are simple to grow provided a few basic guidelines are followed.
All seeds need four elements in order to grow, although not in the same measures; these are temperature, moisture, air, and light. If you’ve purchased a packet of seeds then the back of the packet is generally the first port of call for advice on what that plant requires. However, gardeners often gift or swap seeds. This is a wonderful way to acquire new and unusual varieties but rarely are instructions written down. If you are the lucky recipient of home-produced seed, ask your kind donor what growing conditions work best. Keen gardeners love to share their knowledge and will be eager to give advice.
Seed sowing at a glance
- Take time choosing which seeds to grow - don’t be tempted to buy more than you have the time and space for.
- Annuals, including flowers and vegetables, are among the easiest plants to grow from seed. Their short lifecycle means that they are primed to produce results quickly.
- Most seeds can be sown in spring. Always check the packet for advice on timings but don't worry too much if you are a week or two late.
- All seeds need their preferred combination of heat, moisture and light to grow. They also need time. Some seeds will germinate within 3-5 days, others may take months or need a period of cold before they get going.
- Always sow in a peat-free compost formulated specially for seed sowing.
- Seedlings are extremely vulnerable so give them special care and attention when handling.
While no short guide will tell you everything you need to know about growing plants from seed, here are a few helpful pointers to get you started on your seed-sowing odyssey:
When and where to grow seeds
Gardeners typically sow seed in the spring. That’s because temperatures and light levels are steadily increasing, which promotes seed growth (also known as ‘germination’), often mirroring a plant’s natural lifecycle. Some seeds, particularly hardy annuals and those that require a sustained period of cold before they will grow, can be sown in the autumn.
Some seeds germinate more successfully in the dark. This is easily achieved by covering a pot or tray with compost or a sheet of newspaper after sowing. However, almost all seedlings need bright light once they have started to grow.
‘Moist’ is the watchword when it comes to how much water seeds need. If the soil or compost is saturated with water, seeds may be deprived of essential oxygen or even float away. Later on, over-wet seedlings can rot away at the base - a phenomenon known as ‘damping off’. If the soil or compost is dry, or allowed to dry out after germination, delicate seedlings may quickly wither away. To achieve a good level of moisture, stand containers in a tray of water, let them soak it up until the surface of the compost sparkles and then allow the compost to drain thoroughly before sowing. That way the compost is uniformly moist and will not need watering again for a few days.
Windowsills are often recommended as a good place to germinate seeds but rarely are they bright enough for young plants to continue growing well afterwards. If you use a windowsill, be sure to choose a well-lit one. Turn the seedlings every day, otherwise they will grow vigorously towards the light and topple over. The best place to grow seeds is in a greenhouse, if you have access to one, or in the ground outdoors.
Propagators, heat mats, capillary matting and grow lights are items of equipment used by experienced gardeners to control temperature, moisture and light levels. Cloches and cold frames provide protection from cold, rain and some pests. A beginner can start growing plants from seed perfectly well without any of this kit, but each broadens the opportunity to try something new and different.
Seed packets will often provide different guidance for sowing indoors and directly into the ground outdoors. Experienced gardeners will make their choice based on knowledge, experience and how much space they have available. Sowing seed indoors gives you the best chance of controlling the four conditions they need to grow - temperature, moisture, air, and light. However, not all seeds need pampering: if this were the case we would have no weeds in our gardens! If you have space to sow outdoors and can protect your seedlings from pests, cold, extreme weather and anything that might trample them, then you will often get better results growing them this way. Some plants seriously dislike being moved once they have started growing, particularly those with long ‘tap’ roots.
What to grow seeds in
Another advantage of seed sowing is that very little expensive equipment is required. For indoor sowing, you can use pots or trays manufactured specifically for the purpose, but most of the plastic trays and pots left over from your supermarket purchases can be repurposed very effectively for seed sowing, thereby keeping them out of landfill. The main requirement is that they are reasonably deep (at least 5-6cm), clean and have holes in the bottom to let excess water drain away. The inner tubes from rolls of toilet paper make excellent pots for sowing climbers such as sweet peas, cup and saucer vine (Cobaea scandens), beans and peas.
For indoor sowing, always use a specially-prepared, peat-free seed compost and not garden soil. Although garden soil is miraculous stuff, it’s full of organisms and other seeds that can cause you problems later on down the line. Garden soil can also be a little too coarse, heavy and rich for seedlings to germinate successfully. A good seed compost will be sterile, ‘open’ (light and airy) and low in nutrients. Sterilization removes any microorganisms that might hamper seedling development. Because seeds already contain all the food that a young plant needs to start life, there is no need for compost to be rich in nutrients.
Once you’ve chosen your vessel, whether it be a tray or pot, fill it with compost and level off the surface - if you have another tray or pot of the same size, using the base of that to gently firm and flatten the compost works well.
For outdoor sowing the main requirement is a good ‘tilth’, which is a term that describes the condition of a soil that’s been carefully prepared for seed sowing. Raking the ground to make sure it’s free from weeds, large clods of earth and big stones is essential. Then it’s good practice to make sure the soil surface is level and moist. I prefer to water dry earth thoroughly before sowing, rather than after, especially following a dry spell of weather. If ground is waterlogged, wait for a few days before sowing seed into it.
How to sow seed
If your only experience of sowing seeds is growing cress, then forget everything you know. We sow cress densely because we want to harvest the seedlings very soon after they germinate. If you sow seeds of plants you want to become full-sized specimens in the same way, you will waste seeds, time and effort.
Some large, easy-to-handle seeds such as sweetpeas, sweetcorn, courgettes and cucumbers can be planted singly or in pairs in a pot. The weaker of the two seedlings is often discarded when they start growing to allow the stronger plant to develop fully. Smaller seeds are generally distributed as evenly as possible over the surface of compost or spaced apart in rows in the ground. Do not be tempted to scatter seed thickly as you’ll be wasting money and giving yourself more work to do later when it comes to ‘pricking out’ or ‘potting on’. If you can see the seed easily, try to position each so that there’s at least a centimetre in between. Seed trays divided into individual ‘modules’ are helpful for seeds that can be sown individually.
If seeds are too small for this treatment, scatter them sparingly and try to watch where they are falling to ensure they’re not too crowded. When sowing the tiny seeds of plants such as lobelia and nicotina, it can help to add a little light-coloured sand to the packet to help identify where the seeds have fallen. Planting seed too densely will result in overcrowding, which in turn produces gangly and unhealthy seedlings. Save yourself a lot of effort by sowing ‘sparingly’ as the seedsmen call it.
Cover your seeds with compost or vermiculite (a lightweight, natural mineral used by horticulturalists) if the seed packet recommends you do so. Don’t worry if the seeds are not covered. This is, after all, what happens in nature.
Broadcast sowing, where seed is scattered like chicken feed from waist height, is best suited to large areas such as lawns or meadows. Once scattered, the seed should be gently raked in and protected from birds and rodents where these might be a nuisance.
What happens next?
Seeds can take a varying amount of time to germinate. Some will start to sprout within 3-5 days, others might take 2-3 weeks. A few seeds take months to germinate, but rarely those of annuals, which are eager to get going. It’s important to be both patient and observant when growing plants from seeds. The tell-tale signs of success are the appearance of the first leaf or leaves, known as ‘seed leaves’. If these don’t look like the leaves of the plant you thought you were growing, don’t worry as they rarely do. You might also notice a white or yellowish root covered in fine hairs pointing up from the soil. Resist any urge to correct the seedling’s orientation. They already know which way is up and will soon right themselves.
Once a second set of leaves has formed (and not before), seedlings grown together in trays will need separating out so that they can develop into bigger plants. Gently ease the seedlings from the tray using the end of a plant label and tease them apart. As far as possible, avoid disturbing the roots and handle the seedlings by the ‘seed leaves’ and not the stem or true leaves. Move your seedlings into pots of compost or larger trays for growing on, spacing them 5-10cm apart. Now is the time to use a richer compost, for example John Innes No.2, which includes nutrients to encourage speedy plant growth. At this stage, many plants will tolerate slightly cooler temperatures to those in which they germinated, but should be kept frost-free. Good light remains critical to produce stocky, stable, strong plants.
Seedlings sown outside are not generally transplanted in quite the same way. General practice is to pull out any seedlings that are too close to one another, leaving only the strongest. If you have planted a seed mix, for example of meadow flowers or salad leaves, be slightly circumspect as different varieties in the mix will develop at different rates. If you remove all the weakest seedlings you may find you are left with only one or two of the strongest varieties and you can bet they won’t be the choicest ones!
Keep watering and transplanting into larger pots or trays until your young plants are large enough to fend for themselves in the garden or allotment.
Once you’ve caught the seed-sowing bug, which invariably happens, you can start to try different varieties of the plants you’ve been successful with and experiment with new ones. We all have the odd failure which can be down to all sorts of factors, including old or poor-quality seed, lack of warmth, light, drought or waterlogging. If at first you don’t succeed, attempt to understand what went wrong and try again.
If you are new to raising plants from seed, some of the easiest to start with are annuals. Annuals are plants - including flowers and vegetables - that normally survive for one growing season in the U.K. They grow quickly and offer rich rewards.
For an abundance of flowers I would recommend starting with cosmos, sunflowers, marigolds, cornflowers, calendulas, foxgloves, sweetpeas, poppies and zinnias.
To attract bees and other pollinators, mallow, thyme, teasel and borage could be added to the above. You can find a good range of seeds for pollinators here.
For a reliable crop of herbs and vegetables I would recommend beginning with French beans, courgettes, tomatoes, radishes, sweetcorn, purple sprouting, parsley and chives.