This comprehensive guide to sowing and germinating seeds has been compiled by the team of horticultural experts at T&M. Raising flowers, plants, fruit and veg from seed is a great way to save money and there’s a very special sense of satisfaction that comes from sowing your own!
Whether you want to grow your own fresh produce using our excellent value vegetable seeds or stock up on flower seeds to fill your garden with colour, it’s easy to research your options and order online. Take a look at our complete range of seeds to see how many exciting things you can grow.
Very simply, seeds are embryonic plants waiting to get out. They come complete with their own food supply to start them off, at least until they can put down roots and draw nutrients and water from the soil. All you have to do is provide the correct amount of warmth, light, air and moisture to turn your dormant seeds into living things.
Some seeds are quite unfussy about the conditions that trigger them into growth - many weeds fall into this category. Others are so sensitive they require a carefully controlled environment to germinate. Fortunately, the great majority of flower and vegetable seeds will emerge from their big sleep quite readily, if you follow a few easy guidelines.
All seeds are divided into categories, and to help you germinate them successfully, you’ll need to know which group yours belongs to. Each group is described by a set of initials which is a shorthand way of describing a plant's growing characteristics. Here's a guide to the most common categories:
The actual date when you sow your seeds will vary according to where you live and the seasonal weather. In a cold, late season it’s better to delay sowing. In fact, during cold weather, later sowings often catch up or even overtake earlier sowings that have spent most of their energy just staying alive. Likewise, in cold northern areas you may have to sow several weeks later than in warmer parts of the country, for the same reason.
If you’re not sure when to sow your flower and veg seeds, check our monthly sowing and growing guides for helpful tips.
All seeds need water, oxygen, the correct amount of light and the right level of warmth to germinate. If your seeds need to be started indoors or under cover, it doesn't necessarily mean you have to invest in costly equipment or a heated greenhouse. Supplying enough warmth could be as simple as a temporary home in the airing cupboard or a sunny windowsill.
If you want to take your hobby to the next level, you can invest in an electrically heated propagator. These thermostatically controlled devices deliver the precise temperature for germination using no more power than a 100-watt light bulb.
Here are some tips to help you start seeds under cover:
Direct sowing your hardy annual seeds outside can save time, money and space, but for successful germination you’ll need to prepare the soil and provide the correct growing conditions.
Sowing into seed beds:
Some vegetables, hardy annuals and tree seeds should be direct-sown into a special ‘seed bed’ rather than into their final positions. Here are some seed bed tips:
Direct sowing into final positions:
Of course many hardy annual flower seeds can be sown directly where you want them to flower. Here are some direct sowing tips:
Although most gardens enjoy a summer display of annual flowers, there should always be room for early-flowering biennials like wallflowers and forget-me-nots, as well as the long-lasting perennial flowers that form the heart of the herbaceous border.
Biennials are usually sown in a nursery seed bed where they can grow undisturbed until ready for transplanting. If you sow these seeds in the spring, the resulting plants will be sturdy enough to be moved to their flowering positions in autumn just as the summer bedding plants are finishing.
Sow the seed in straight drills and keep the bed watered during dry spells and weeded at all times. An occasional feed with a liquid fertiliser can be given during the early stages of growth, but refrain from feeding for at least six weeks before transplanting to avoid sappy growth that could be damaged by hard frost.
Some perennials can be treated as half-hardy annuals and sown indoors early in the year using a propagator, greenhouse or warm windowsill. They can be transplanted in late spring and should flower during the summer.
However, the majority of perennials including the stately lupins, hollyhocks and delphiniums, can be grown in the nursery bed in spring, transplanted to their permanent positions in the border in the autumn, and will flower the following season.
Remember that these plants will lose their leaves in late autumn so it’s a good idea to mark the planting position with a label or stake. And unlike annuals which complete their life cycle in one year, perennials will occupy the same site for years, so thorough preparation of the soil is important to ensure the plants enjoy a long and healthy life.
Tiny seeds such as begonia and calceolaria can be difficult to handle. Sometimes, the foil packet seems to contain nothing except a trace of dust-sized particles! Here are some tips to help you sow tiny seeds:
Some seeds benefit from pre-treatment before sowing, or from being sown in a particular way. This pre-treatment is rarely vital to success, but your seeds might take longer to germinate if you don’t do it.
Soaking is beneficial in two ways; it can soften a hard seed coat and also leach out any chemical inhibitors which might prevent germination. Anything from 1-3 hours in water which starts off hand-hot, is usually sufficient. If soaking for longer, the water should be changed daily.
Some seeds swell up when they’re soaked. If any seeds in your soaked batch swell within 24 hours they should be planted immediately and the remainder pricked gently with a pin and returned to soak. As each seed swells, remove and sow before it has time to dry out.
Some seeds have a combination of dormancies and each one has to be broken in the right sequence before germination can take place. For example some lilies, tree peonies and Daphne need a warm period during which the root develops, followed by a cold period to break dormancy of the shoots, before the seedling actually emerges. Other seeds need a cold period followed by a warm period and then another cold period before they will germinate. In all cases, the times and temperatures will be provided in the sowing instructions on the packet.
On some seed packets you will find a reference to 'pre-chilling', or stratification. This is a pre-treatment which can speed up the germination of otherwise slow-to-germinate seeds. However, even after pre-chilling some seeds can stubbornly refuse to germinate until a year or more has passed, so never be too hasty in discarding them.
Pre-chilling was traditionally done by standing the pots outside in a cold frame during the winter. It’s often quicker to adopt the following technique:
When seeds germinate, the first leaves to appear are the cotyledons or seed leaves. These are usually a pair of oval, fleshy leaves that bear no resemblance to the mature leaves of the plant. The traditional advice is that seedlings shouldn’t be pricked out or transplanted until the first true set of leaves appear, but wait until you’re confident that they’re large enough to handle.
Removing the tiny seedlings from the sowing tray into containers of a good universal compost can be a delicate business. Here are some tips:
Once your seedlings have been pricked out, potted on and have become big enough for you to think about planting out, you’ll need to ‘harden them off’. This means gradually acclimatising them to the harsher conditions of the great outdoors. Allow a minimum of ten days to do this, preferably longer.
Damping off is one of the most common and troublesome types of garden diseases. It can affect all types of seedlings, but is most problematic on fast-growing flower seedlings (like antirrhinums, lobelias, nemesias, petunias, salvias and stocks) or vegetable seedlings like cabbages, cress, lettuces, tomatoes, peas and beans. Some slow-growing trees and shrubs are also prone to grey mould forms of damping off.
The symptoms of damping off are varied, but all result in the death of the seedling. Young seedlings can develop circular patches and collapse, the stems can shrivel, or the root system can simply rot away. Sometimes larger seedlings or young plants develop leaf spotting or discoloration, and some develop patches of grey mould on the stems or leaves.
The organisms that cause damping off are varied, but most are soil-borne. Prevention is the best line of defence so good hygiene is vital. Only use cleaned and disinfected pots and seed trays and make sure that greenhouse benches are sterile. Clean and disinfect water storage tanks regularly, but try to use tap water for susceptible plants. Also use a good quality, sterilised seed compost, which is moist but not over wet. Don't assume all bought compost is sterile, as most is not.
Try to avoid waterlogging and high humidity, as this makes seedlings more vulnerable to attack. Sow seed thinly and prick out as soon as possible, handling the seedlings by their leaves, not stems. Do not re-use any compost that has been affected.
Visit our comprehensive collection of pest and disease guides to troubleshoot other problems with your plants.
For an easy chart to help you see when and where to sow some of our most popular veg and herb seeds, download our quick guide now.
Alternatively, click on the image below to view it as a full size image online:
Good luck with your seed sowing journey. Share your successes with us over on social media. We love to see your photos!