Popular members of the allium family, onion and leek seeds require little more than a sunny windowsill to start them off. Rewarding and cost effective, onions raised from seed are often bigger than those grown from sets - ideal if you’re hoping to win a prize at the village show! Here’s everything you need to know about growing onions, spring onions, shallots and leeks from seeds.
For the best results, start your onion and shallot seeds off indoors, around February or March. An early sowing extends the growing season, allowing more time for your onions to grow large.
If you don’t have space to start them off indoors, you can sow your onion seeds directly outside in March and April. They need to be growing strongly by the time the weather warms up at the end of spring to give the bulbs a chance to swell. Simply sow your onion and shallot seeds in shallow drills outdoors, about 1.3cm (½inch) deep. Mark out rows, spaced about 20cm (8 inches) apart, with string tied between canes. This will remind you where they are when you come to plant out other crops! To give them more room as they grow, thin your seedlings to about 10cm (4 inches) apart, using the thinnings as salad onions.
Growing onions and shallots from seed gives you the chance to try varieties that can’t be bought in the supermarket. For onions, the classic award-winning ‘Red Baron’ produces a deep red-rimmed shiny bulb, while ’Globo’ can produce bulbs up to 1kg in weight! And if you’re after variety, try a premade seed mix like our ‘Four Colour Bulb Mix’.
If you prefer the more delicate taste of shallots, ‘Figaro’ produces lovely banana shaped bulbs with distinct flavour and clean white flesh. For a variety with good bolting and mildew resistance, try ‘Lorient’ which produces teardrop shaped bulbs with blush-coloured flesh and a lovely sweet flavour.
Spring onion seeds can be sown directly outdoors from March, and you can continue to sow them every three weeks until August for regular crops throughout the summer. Taking up very little room and ideal for containers, you don’t have to worry too much about spacing as spring onions develop much smaller bulbs, if any at all. Some of our favourite varieties include:
If you want a very early spring harvest, try sowing a batch of the quick growing and hardy variety ‘White Lisbon’ in September. With an RHS Award of Garden Merit, it’s one of the best varieties for overwintering.
Sow your leek seeds outdoors in March and April for harvests from late September through to January. Because they take up quite a lot of space, many gardeners start them off in seed beds for a few months until they’re ready to move to their final positions.
Leeks are hardy and can be left in the ground until required. ‘Musselburgh’ and ‘Below Zero’ F1 hybrid are especially cold tolerant varieties, making them a great choice for areas with snow during the winter. For an exceptionally long cropping season, try ‘Northern Lights’. The leaves of this attractive leek change from blue-green to a stunning shade of purple as the weather gets colder.
Sow onion and leek seeds for a cost effective crop to liven up your favourite meals. If you don’t have the space to sow your own seed, then take a look at our guide to growing onions and shallots from sets. Find other popular alliums to grow, growers guides, and our full range of products at our onions, garlic and shallots hub page. Keep us up to date with your allium harvest via social media! We love to hear from you.