How to grow Onions and Shallots

Given the right conditions, onions and shallots are very easy to grow and reward little effort with a good crop. They’re one of the most versatile vegetables in the kitchen, too. Onions are a large family of strongly flavoured biennial and perennial plants. Depending on when and how you grow them, you can achieve a crop that can be harvested from as early as June right up until October, and many varieties, such as Sturon and Stuttgarter Stanfield, will keep until the following spring.

Onions and Shallots are raised either from seed, plants or from sets (small bulbs), each has pros and cons:
Onion & Shallot Sets - Advantages – easier to grow, less prone to pests and diseases, matures earlier. Disadvantages – less choice of variety, more prone to bolting, more expensive.
Onion & Shallot Seed - Advantages – available for all varieties, less prone to bolting, more flexible sowing times, cheaper. Disadvantages: more labour, longer growing season, more susceptible to pests and disease.
Onion & Shallot Plants - Advantages – easier to grow, less prone to pests and diseases and have had a head-start on arrival, meaning a shorter growing season for you. Disadvantages – Less choice of variety, more expensive. 

Growing Autumn Planting Onions and Shallots

These onion and shallot varieties you plant in autumn for a crop in mid-summer the following year. The advantage of these varieties is that you are planting in soil that has been naturally warmed up over the summer, so they settle well and they are set up to tolerate cold winters.

Placing Autumn-planting Onions and Shallots
In September to November plant sets pointy side up straight into the soil outdoors at 7-10cm (3-4in) intervals in a row, and space rows at 30cm (12in) apart in an open, sunny site in fertile soil that is well-draining yet moisture retentive. Incorporating bulky compost into the soil in the spring before will achieve this by upping its fertility levels and creating a good soil texture, without it being too rich.

Feeding Autumn-planting Onions and Shallots
Apply bulky compost earlier in the season to planting- this will increase the fertility of the soil without it being too rich which would be the case if freshly incorporated compost is added. In spring, you can boost post-winter growth by apply a seaweed-enhanced feed, rich in phosphorous for stimulated root growth to encourage full and flavoursome bulbs.

Watering Autumn-planting Onions and Shallots
Water at planting in autumn and reduce watering overwinter. In spring water lightly as the weather warms but stop again once the bulbs are actively swelling. A well-textured soil with incorporated bulky compost will hold on to enough moisture to see the crop through the overwintering and growing season.

Temperature of Autumn-Planting Onions and Shallots
You can plant sets straight into the open soil in autumn as the ground has been adequately warmed up over summer. Bulbs will appreciate an open and sunny site. If exposed to temperatures that are too low, there is a risk of bolting which means that plants produce flowers at the expense of harvestable bulbs. Varieties that are suited to autumn-planting are hardier to cold temperatures and less prone to bolt.

Harvesting and storing Autumn-planting Onions and Shallots
Harvest bulbs from early to mid-summer (June to July). For shallots lift with a border fork once you notice the leaves have gone yellow. Separate the clusters, clean off soil and grit, and dry in a cool light place for one to two weeks. In wet weather bring into a garage by the window. In dry, sunny weather leave outdoors or in a well-ventilated greenhouse. For onions, lift when the foliage has wilted and yellowed. Lift carefully with a border fork, dry in a cool, light place for two to three weeks before using in the kitchen. Store in a cool place – plaiting onions and hanging them is a space-saving way to keep them drying, and off the ground away from pests.

Best Varieties of Autumn-planting Onions and Shallots - Onion ‘Red Cross’, Onion ‘Radar’, Shallot ‘Yellow Moon’Shallot ’Biztro’

Pests and Diseases of Autumn-planting Onions and Shallots - Onion fly, Bulb rot, Smut, Shanking

Growing Spring Planting Onions and Shallots

These onion and shallot varieties you plant in spring for a crop in late-summer to early-autumn that year. The advantage of these varieties is that you have a store of flavoursome onions over the winter when home-harvests of other crops are low. Heat-prepared sets have been treated to prevent bolting, which is when the onions flower at the expense of producing harvestable bulbs.

Placing Spring-planting Onions and Shallots
In March and April plant onion sets pointy side up straight into the soil outdoors at 15cm (6in) intervals in a row, and space rows at 25cm (10in) apart in an open, sunny site in fertile soil that is well-draining yet moisture retentive. Incorporating bulky compost into the soil in the autumn/winter before will achieve this by upping its fertility levels and creating a good soil texture, without it being too rich.

Feeding Spring-planting Onions and Shallots
Apply bulky compost earlier in the season to planting- this will increase the fertility of the soil without it being too rich which would be the case if freshly incorporated compost is added. In late spring, you can boost post-winter growth by applying a seaweed-enhanced feed, rich in phosphorous for stimulated root growth to encourage full and flavoursome bulbs.

Watering Spring-planting Onions and Shallots
Water at planting in spring and more so as the weather warms as the season continues. Stop again once the bulbs are actively swelling. A well-textured soil with incorporated bulky compost will hold on to enough moisture to see the crop through the growing season.

Temperature of Spring-planting Onions and Shallots
You can plant sets straight into the open soil in spring. Bulbs will appreciate an open and sunny site. If exposed to temperatures that are too low, there is a risk of bolting which means that plants produce flowers at the expense of harvestable bulbs. Heat treated spring-planting varieties are less prone to bolt and flowering at the expense of producing harvestable bulbs.

Harvesting and storing Spring-planting Onions and Shallots
Harvest bulbs from late summer to early autumn (August to September). For shallots lift with a border fork once you notice the leaves have gone yellow. Separate the clusters, clean off soil and grit, and dry in a cool light place for one to two weeks. In wet weather bring into a garage by the window. In dry, sunny weather leave outdoors or in a well-ventilated greenhouse. For onions, lift when the foliage has wilted and yellowed. Lift carefully with a border fork, dry in a cool, light place for two to three weeks before using in the kitchen. Store in a cool place – plaiting onions and hanging them is a space-saving way to keep them drying, and off the ground away from pests.

Best Varieties of Spring-planting Onions and Shallots - Onion ‘Red Fen’, Onion ‘Red Baron’, Onion ‘Stuttgarter Stanfield’, Shallot ‘Jermor’

Pests and Diseases of Onions and Shallots - Onion fly, Bulb rot, Smut, Shanking

 

How to Grow Onions and Shallots from Plants

When to plant: April

Harvest time: August – September

Planting: Onion plants are delivered in early April when they’re ready to be planted outside. Make sure the soil is well dug and crumbly before planting. Remove the plants from each cell one at a time by pushing them out from underneath. Using a dibber, create drills (the same depth as the plant cell) in rows at a spacing of 15cm. The plants should be planted no deeper or shallower than they were in the cell tray. Firm them into the ground and water-in.

 

How to Grow Onions and Shallots from Seeds

When to Sow
Autumn sowing onions: August – September
Spring sowing onions: January - March
Spring sowing shallots: January – March

Harvest Time
Autumn sowing onions: June – July
Spring sowing onions: August – September
Spring sowing shallots: August – September

Sowing
Autumn-sowing onions can be sown indoors to be transplanted outside at a later date, which will give them a bit of a head start, or they can be sown directly into the growing position. Spring-sowing seeds are usually sown directly into their growing position.
Sowing indoors: For an earlier start, especially in colder areas, sow seed in a cool greenhouse in late winter or early spring. Once the seeds have germinated and are about 1cm tall and at ‘crookneck’ stage, they should be pricked out at a spacing of about 5cm. Start to harden them off once they reach 2-3 leaf stage before planting out into eventual growing position in mid – late spring. Transplant the seedlings into rows outside in mid – late spring, at a spacing of around 15cm, or allow up to 25cm for larger bulbs.
Sowing outdoors: As soon as the soil is workable in spring, or before it becomes in mid-autumn prepare it by digging and raking it to a fine texture. Avoid sowing into very cold or wet soil. Sow thinly into rows at a depth of about 2cm. The rows should be about 30cm apart from each other. As the seedlings start to grow they will need to be thinned every now and then to create space for bulbs to develop. Use the removed seedlings as spring onions or chives. Once they reach a spacing of about 15cm you’ll no longer need to thin them.

 

How to Grow Spring Onions
When to sow
Spring Onions: March – July
Winter Hardy Spring Onions: August – October

Harvest time
Spring onions: May – September
Winter hardy spring onions: February – May

Sowing
Sow winter hardy spring onions, such as White Lisbon, in autumn and spring varieties from March. You can continue to sow spring onions throughout summer to provide a continuous harvest. Prepare the soil by digging and raking it to a fine, crumbly texture. Avoid sowing into very cold or wet soil. Sow thinly into rows at a depth of about 2cm. The rows should be about 10cm apart from each other. As the seedlings start to grow they will need to be thinned every now and then, but whatever you remove doesn’t have to go to waste. You can use the removed seedlings as spring onions or chives. Once they reach a spacing of about 2cm, you’ll no longer need to thin them out.

For Best Results

Try our onion fertiliser, which is specially formulated to give onions all the nutrients they need to produce healthy growth.

You May Also Need

The Great Little Weeder – perfect for weeding between rows!
Onion Storage Nets – perfect for keeping onions in top condition!
Onion Hoe – specially designed to keep your onions weed-free!

 

 

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