Onions & Shallots

How to grow onions

Grow your onions using sets from Suttons. Sets are small, young onions that are heat-treated before sale, which helps reduce bolting (flowering) in the summer. Plant your sets in autumn or spring depending on the hardiness of the variety you choose.

Unpack your onion sets on arrival and store them in a light, cool position until planting time. For spring planting onions (between February and April, as long as risk of frost is passed), follow these guidelines:

• Spacing: Allow 10cm (4") between sets and 30cm (12") between rows.
• Planting Depth: Push the sets into the soil so only the very tips are visible – but firmly enough that birds can’t easily pull them out.
• Pest Protection: Cover your newly planted sets with netting to stop pigeons from digging them up.
• Weed Control: Gently hoe between the rows to keep the area weed-free as they grow.
• Quantity: 250g of sets will plant a row of approximately 6m (19').

You can also grow your onions from seed. Sow your onion seeds in early to mid spring in a tray of fine seed compost. Place the tray in a sheltered place until germination happens and your seedlings are large enough to plant out into rows in the veg patch.

How long do onions take to grow?

Plant autumn planting onion sets in October to be ready to harvest the following July. Onions need around four to five months to develop good sized bulbs from sets. More cold tolerant varieties like the red skinned onion ‘Electric’ and yellow onions ‘Senshyu’ happily overwinter in the garden when not much else is growing. Onion seeds take around four months to mature to a harvestable size.

What's the difference between onions and shallots?

Onions typically form a single, larger bulb with a pungent, sharp flavour. Shallots grow in clusters, forming multiple smaller bulbs from a single set. Although they’re very closely related to each other, and in the same plant family shallots like ‘Longor’ can be multi-bulbed, and are often smaller or longer and thinner than onions. They both grow in the same way and can be used in similar dishes, along with garlic bulbs.

How to plant shallots

Plant shallot sets in a sunny position into well drained, fertile soil. Push the sets into the soil, leaving the very top visible above the soil and around 10 cm between each set. Water in using a rosette to avoid disturbing the bulbs. Water every week during the growing season and more often in hot weather.

Grow shallots from seed by sowing under cover from January or outdoors from April. Sow seeds into seed trays of fine, damp compost or thinly along rows in the veggie patch. Keep your seedlings moist as they develop. The banana-shaped shallot ‘Jermor’ has fantastic flavour grown from seed.

What are 'sets' and why should I use them?

'Sets' are small, immature bulbs from the previous season's harvest. They have been heat-treated to prevent them from flowering ('bolting'), which channels the plant's energy into producing a larger bulb instead of seeds. They are the easiest and most reliable way to guarantee a successful crop.

When should I plant and when can I harvest onions & shallots?

This depends entirely on the variety:

• Plant Autumn-planting varieties between September and November. They will establish over winter and are typically ready to harvest from June to July the following year.
• Plant Spring-planting varieties between February and April, once the risk of hard frost has passed. These will be ready to harvest from late summer into early autumn.

Harvest when the foliage starts to yellow and flop over. Choose a dry day to lift the bulbs, and leave them on the soil surface to dry in the sun for a week or two before storing.