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