Overwintering Onions: How to Plant Onions in Autumn for an Earlier Harvest
As the night start drawing in and the temperatures begin to drop, it’s time to think about getting your overwintering onions growing. They can be a very economical use of space within the vegetable garden, with the added bonus of being a pest deterrent. It’s very easy to overwinter onions, but here are a few things to know before you get going.
The Benefits of Overwintering Onions
One of the biggest benefits of sowing overwintering onions is that they will be ready around a month earlier than their spring-sown counterparts. This is because sowing them in autumn gives your onions a head start when it comes to establishing roots. When the warmer spring weather arrives, your onions are ready to jump into action thanks to the slow development of their roots over the winter period.
This earlier harvest will allow you to get a second crop in such as sweetcorn or winter squashes that need planting out later in the season.
Onion Sets vs Onion Seeds
Onion sets are small, dormant bulbs that have been grown from seed and harvested early, meaning you don’t need to worry about the early parts of the growing process. In the UK, they are usually planted in early to mid-autumn, giving them time to establish before the colder winter weather arrives. You will find a greater selection of varieties available as onion seeds, but sets are certainly the easier option for growing onions.
Find out more about how to plant onion sets successfully in our guide here.
How to Sow ONION SEEDS for overwintering
To sow onion seeds for overwintering, you want to sow them in module trays in good-quality compost following the sowing instructions for your specific variety. Senshyu Yellow is a fantastic variety for this time of year, whilst Red Baron can be very successful in milder UK areas. Gently water the seeds to avoid displacing them. Onion seeds generally germinate best in relatively cool conditions, so avoid leaving your trays somewhere that gets too hot. You can transplant your seedlings to their final outdoor growing position once they develop true leaves and a healthy root system. Be sure to protect them with something like horticultural fleece if the temperatures drop.
Tips for Growing Overwintering Onions
There are a few things that are important to keep in mind when it comes to overwintering onions.
- There are specific varieties of onion that are meant for either autumn or spring sowing, and they are not the same. Make sure to choose the right varieties.
- Your onions will need plenty of drainage. Overwintering onions are cold hardy within reason, but they will not tolerate sitting in waterlogged soil. Think about your growing position carefully, particularly if you have heavy soil. Working in well-rotted organic matter can improve the soil structure, while horticultural grit can also be incorporated to improve drainage. If your soil is particularly prone to waterlogging, consider growing your onions in a raised bed or another area with good drainage. Onions left sitting in persistently wet conditions are likely to rot or become diseased.
- Your onions are unlikely to need watering throughout the winter. But keep an eye on them when spring comes, especially if it’s particularly dry.
- Overwintered onions don’t generally store well so are best consumed within 2-3 months of harvest. For onions that will store longer, spring-sown onions are generally a better choice.
- Birds can frustratingly pull out your freshly planted onion sets while looking for worms, so consider using our protective netting tunnels or horticultural fleece to prevent them from digging up your onions.
We’ve selected a great range of overwintering onion sets for you to choose from. From the ever-popular Shakespeare to the beautiful red Akado, these onions are perfect for planting now. Our collections also offer great value for money, combining some of our favourite varieties of onions, shallots, and garlic to make choosing your overwintering options easier.
What are you waiting for? Check out our full range today!
