One of the most versatile vegetables on the plot, growing your own onions means you’ll always have a home-grown stash at hand!
All you need to grow onions is a sunny, sheltered area to grow in with well-draining soil - raised beds, veg plots or deep containers (with a minimum of 6 inches of soil depth) are perfect. We always use the Quadgrow Root Veg Planter for our onions.
Growing from Sets
Onion sets are planted in March and May, and love a sunny well drained position to grow in. Sets are second season onions that have been grown from seed during the previous season. These can be planted 1-2 months earlier than seeds, to give an earlier harvest. As onions are biennial they will flower in their second season, so if growing from sets you may have trouble with bolting if the summer is particularly wet or cold. An onion which has bolted is perfectly edible, but it will not continue to grow once a flower spike has been produced, so the bulbs will be smaller and won’t store as well. Onion sets should be planted directly into the ground – space them 10cm apart and gently push into the ground so that only the tip of the bulb is showing.
Growing from seed
It’s easy to grow onions from seeds, but to get a mature onion before the end of the season you will need to start the seeds in February.
Growing from seed gives a much greater choice of varieties and is often much cheaper than buying sets. Onions grown from seed are much less likely to bolt. Our favourite variety is ‘Setton’ AGM.
- Sow seeds 1cm deep in rows, they can be sown directly into the ground or planter which is at least 10cm deep. We grow ours in a Large Salad Planter or Root Veg Planter.
- As the seeds germinate, thin any weaker seedlings out to 5cm gaps between the plants.
- As the stems begin to thicken, thin out the rows so that there is 10cm between each plant.
- Feed and water with a complete feed throughout the season especially during dry periods. An additional high potash feed in June will help ripen the bulbs. Nutrigrow is the balanced feed we use, but there are also organic fertilisers.
- The bulbs are ripe once the foliage begins to turn yellow and fall over in late summer. Harvest by lifting with a fork, do not pull them by the stem as this can damage the bulb.
- Onions intended for storage should be firm and disease free before drying for 3 weeks.
Onion fly can be an issue when growing onions from seed, these insects will lay their eggs at the base of shoots. Once they hatch the larvae will begin eating away at the bulb causing the leaves to wilt and die. To prevent the insect laying its egg on the plant cover with insect netting.
- ‘Ailsa Craig’ - Good show quality variety due to the consistent shape, colour and large size.
- ‘North Holland Bloodred Redmate’ - Reliable red onion can be harvested early and used as a salad onion or thinned out and harvested as a bulb onion. Has a crisp sweet taste.
- ‘Sturon’ - High cropping variety, one of the best onions for storing.
If you have any questions about growing onions, give one of our Gardening Angels a call 0845 602 3774 or send us an email firstname.lastname@example.org.