It's easy and rewarding to grow plants from seed. With a few packets of seeds, some compost and a bit of patience, you can fill your garden with flowers and your plate with home-grown vegetables. Follow our step-by-step guide and find out how to plant sunflower seeds, zinnias, tomatoes and other popular garden plants.
Growing plants from seed is one of the most satisfying parts of gardening. There's something magical about watching a seed germinate and nurturing seedlings as they grow into plants. I find the process of growing flowers and vegetables just as rewarding as the end result. Seeds are also the cheapest way of growing a large number of plants for your garden. If you collect seeds and use your own compost, you can even grow plants for free.
Planting seeds is straightforward, but you do need to get the timing right, and seeds often need specific conditions in which to germinate. This guide covers everything you need to know to successfully grow plants from seed.
How to choose your seeds
Honestly, the hardest part about growing plants from seed is deciding which plants to grow! Unless you have a vast garden (and a lot of time) you'll need to narrow down your choices. Grow the flowers you love to look at and the vegetables you enjoy eating. I used to grow runner beans, but my family didn't particularly like them, so they ended up getting stored in – and later thrown out of – the freezer. Now I grow French beans instead, as I know they'll get eaten.
You can try growing tomatoes, peppers, pumpkins and other vegetables using seeds from vegetables you've bought to eat, but it may not be as successful as planting seeds from a packet. Buying vegetable seeds gives you access to many varieties, most of which will taste a lot better than those mass-produced for supermarkets.
When choosing flower seeds, pick flowers that are compatible with your garden. You need to take into account your soil type and how much sun they'll get when you plant them out. Some of the easiest flowers to grow from seed are marigolds, nasturtiums, calendula, sweet peas, cosmos, zinnias and sunflowers.
Heirloom plant seeds are non-hybrid varieties of plants (usually vegetables) that have been grown true-to-type for several generations. Heirloom vegetables don't necessarily taste better than hybrids, and they can be trickier to grow, as many hybrids have been bred to be disease resistant or to produce higher yields.
When to plant seeds
Timing is everything when it comes to planting seeds. Plant them too early and you'll run out of storage space before it's warm enough to move them outside. Plant them too late and you'll miss out on early season blooms. With some flowers, like sweet peas, it's worth planting several batches a couple of weeks apart, as this gives you a longer flowering season. But if you have limited space or are growing plants like marigolds that last all season, you may not want to commit to looking after that many baby plants.
To determine when to plant seeds in the UK, you need to work back from your last frost date. This can vary from mid-March to the beginning of June, depending where in the country you live. Check the average last frost date map on PlantMaps to find an estimated date for your local area. This isn't an absolute date; there will be years when you get a late cold snap and years when the weather is milder earlier.
Seed packets highlight the months when you should sow seeds and the months when you can plant seedlings outside. If you live in a warm area, such as central London, you'll be at the earlier end of this timescale, whereas if you live in the Scottish Highlands, you'll be sowing and planting later.
Some seeds, like nasturtiums, don't like being transplanted and are best planted outdoors where you want them to grow. When planting seeds outside, you'll need to wait until the soil has warmed up and the weather is unlikely to give you any nasty surprises. You can cover beds with cloches or cardboard to warm them up in advance.
Early spring is the busiest time of year for sowing seeds but not the only time. Biennial flowers, like foxgloves, are sown in summer, and hardy annuals and winter veg are often soft in the autumn.
How to plant seeds
You only need a few basic items to plant seeds:
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Seed trays or pots: Seed trays or modular trays are readily available, but you can also recycle yogurt pots, plastic food trays, toilet roll tubes or newspapers. Plastic-free options include cardboard pots, wooden seed trays and wool pots.
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Compost: You can use a specialist seed and cutting compost or run some multi-purpose compost through a sieve.
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Plant labels: Wooden lollipop craft sticks (or sticks from ice lollies!) work fine, but you can also use metal or slate markers. If you have none of these, you can just stick a piece of paper onto the seed tray.
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Plastic or glass cover: A propagator helps raise the temperature and keep the air humid. If you don't have a propagator, you can use a plastic food tray bag. A glass cover can also work, though you may have to check your seeds more often so they don't dry out.
You'll also need a bright, warm place to keep your seeds, such as a sunny windowsill, conservatory or greenhouse.
If you're using seeds you've saved from previous years, check the expiry date before planting. It's tempting to use up old seeds first, but you risk wasting time and effort on seeds that are unlikely to germinate.
Step-by-step guide to planting seeds
Step 1: Pre-planting
You can sow most seeds without any pre-treatment, but soaking and/or scarifying certain seeds can improve germination rates. This is particularly true for seeds with thick outer shells, such as peas, beans, corn, sweet peas, nasturtiums and Ipomoea (morning glory).
To scarify a seed, simply nick the outer coat with a sharp knife. This lets air and water in which helps the seed germinate. To soak seeds, either immerse them in water for up to 24 hours or place seeds inside a damp, folded paper towel and put them inside a plastic tub (like a takeaway container) or bag.
Whichever method you use, soaked or scarified seeds should be planted immediately.
Step 2: Fill your trays
Select an appropriate tray or pot for your seeds and fill it with peat-free compost or coconut coir compost. If you're using yogurt pots or plastic trays from your recycling bin, make sure there are draining holes in the bottom before filling them.
Larger seeds, such as pumpkin, cucumber and courgette seeds, are best planted in individual modules, but many flower seeds can be planted in a tray and pricked out once seedlings develop. I recommend planting sweet pea seeds in deep pots or toilet roll tubes so they can develop strong roots.
Step 3: Sow your seeds
Some seeds require light to germinate and need to be on or near the surface of the compost. Others need darkness to germinate and must be planted deeper. As a general rule, the larger the seed, the deeper you plant it. When planting flat seeds like cucumber, courgette, melon and pumpkin seeds, plant them on their edge to reduce the risk of rotting.
Step 4: Water and label
Place your pots or seed trays on a larger tray which will catch any excess water, then gently water the seeds. You want to keep the compost moist but not waterlogged. Label your seeds with the name of the plant. You may also want to add the date if you're planning on sowing more seeds at a later date.
Step 5: Cover and wait
Cover the seeds with plastic or glass to help keep moisture in and place them somewhere warm and bright. Most seeds need the soil temperature to be at least 7°C to germinate, but tender plants require higher temperatures; for example, when growing chilli plants from seed, the ideal temperature is between 23°C and 30°C. Check the back of your seed packet for information on planting depth and temperature requirements.
If you're planting seeds early in the season, a heated mat or propagator and grow lamp can help you grow strong seedlings.
How to plant seeds outdoors
If you don't have anywhere suitable to plant seeds indoors, you can sow seeds directly outdoors in spring or early summer. This is also the best option for plants that don't like to be moved, for example nigella, nasturtiums, poppies, spinach, radishes and carrots. Prepare your soil by removing any weeds, digging in compost if necessary, and breaking up and raking the soil to create a fine, even surface.
You can either sow your seeds in drills (the usual approach when planting vegetable seeds) or scatter them for a more natural effect (for example, when planting wildflower seeds). When scattering seeds, mix them 50/50 with sand to bulk out the mix and make it easier to sow them evenly. Once you've scattered the seeds, lightly rake the soil.
Sowing in drills is a better option if seeds need to be planted deeper. Use a cane, hoe or dibber to make a narrow trench (drill) to the correct planting depth. Lightly water the soil and plant seeds along the base of the drill. Check the back of your seed packet for information on spacing. Rake the soil back over the seeds and water. Don't forget to mark where you've planted them!
When to transplant seedlings
If you've planted seeds in seed trays, you'll need to separate the seedlings into individual pots to prevent overcrowding. This is called "pricking out". Wait until the seedlings have their first "true leaves" (actually the second pair of leaves to develop) and are large enough to handle before transplanting them.
Water the seeds before filling the pots or seed module tray you'll be moving them to with compost. To remove each seedling from the tray, hold it by its leaves and use a pencil or dibber to carefully ease the seedling's roots up out of the soil. Make a hole in the new compost and place the seedling into an individual pot or cell of a module tray. Gently press the compost around it and water it. Don't forget to label your pots!
When to plant out seedlings
Before planting seedlings outside, you need to be confident that the weather is warm enough. Some cold-tolerant plants can survive a late frost, whereas other less hardy plants need night-time temperatures to be above 10°C. Be wary of planting out tender plants too early in the season, especially if the long-range weather forecast is uncertain.
Before planting out flowers or vegetables, you need to let them acclimatise to outdoor conditions. If you don't harden seedlings off properly, you risk shocking the plants, which can stunt their growth or even kill them.
How to harden off seedlings
Hardening off plants is done in stages, and the whole process may take two or three weeks for tender plants. The warmer the environment you've raised the seedlings in, the longer the hardening off period needed. Your seedlings need to get used to colder and more changeable temperatures, strong sunlight, wind and rain.
If your seedlings are used to a heated greenhouse or indoor environment, you'd ideally move them to a cool greenhouse or cold frame before leaving them outdoors. If you don't have a greenhouse or cold frame, find a sheltered, warm spot, such as in front of a south-facing wall or fence, and use pots or a piece of wood as a windbreak if needed. Protect your seedlings from strong sunlight and heavy rain.
To begin with, leave the plants out for just a few hours, extending the time each day until by the end of the first week, they're out all day. If you don't have a cold frame or greenhouse, you may need to cover your plants with fleece at night. Then gradually remove the fleece layers as they get used to the cooler temperatures. Once your plants are accustomed to outdoor life, you can plant them out into your garden.
How to protect plants from late frosts
Even if you've hardened your seedlings off correctly, they could still get damaged by an unexpected late frost. Keep a close eye on the weather forecast after transplanting your seedlings and cover the plants with a layer of fleece or a cloche if the temperatures look likely to plummet or strong winds are predicted.
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FAQ
What do you need to plant seeds?
All you need to plant seeds is some compost, a pot or tray, a plastic cover and the seeds themselves. You can buy seed modules, trays or biodegradable cardboard pots, but you can also repurpose toilet roll tubes, yogurt pots and plastic fruit trays. Just make sure the container has holes in it for drainage.
When should you transplant seedlings?
Transplant seedlings from a seed tray into their own pots when they've developed their first set of true leaves (the leaves that follow the seed leaves). When planting seedlings outdoors, wait until the risk of frost has passed and the weather is warm enough for the plants to thrive.
How do you plant tomatoes from seed?
Tomatoes are one of the easiest plants to grow from seeds. Fill a seed tray or pot with compost, place the seeds on top and cover with about half a centimeter of compost. Tomatoes need a temperature of around 18°C to germinate, so either use a heated propagator or cover the pot with a plastic bag or tray and leave it in a warm, sunny place.
How do I plant marigold seeds?
You can plant marigold seeds outside after the last frost or inside earlier in spring to give the plants a head start. When planting marigolds inside, plant seeds in individual seed modules or scatter them across a seed tray and cover with half a centimeter of compost. Leave the seeds in a warm place to germinate and prick them out or pot them up after the first true leaves have appeared. Wait until all risk of frost has passed before planting your seedlings outside.
How do you grow apple trees from seeds?
It's possible to grow an apple tree from seed, but it will take many years for the tree to produce fruit – if it produces any at all. Unless you're growing it for a challenge, you're better off buying an apple tree instead. Apple seeds require a period of cold stratification in order to germinate. You can mimic this by placing the seeds in a damp paper towel and putting them in the fridge for several months. Once the seeds have sprouted, you can plant them in a pot of compost.
