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