Do you know your onions? I don’t, so I have been seeking advice from someone who does. Grandpa Haxnicks is going to guide me towards a healthy crop of container-grown onions that will have me crying with pride and joy.
You can grow onions from ‘sets’ or from seed. Sets are small immature onions that can be planted directly into the soil in March or April. Despite being drawn to small, immature things I have decided that I will have a go at growing from seed as it is far cheaper . Grandpa Haxnicks has given me a few tips for success. Success will be judged on how many tears are shed after harvest.
You will need to fill a seed tray filled with a good multi-purpose compost. Sow the teeny-weeny onion seeds approx 1cm apart and lightly cover with a thin layer of compost. They will need a temperature of 20-25˚C to germinate, so make sure that they are placed on a warm, sunny windowsill or in a heated greenhouse. The seed trays can be placed in a clear plastic bag or covered with cling film to help maintain a warm, moist environment for the seeds to sprout. After approximately 8-10 days little green lassos will emerge from the soil. Onion seeds can do a poor job of pulling away from their seed husk so you can always give them a little helping hand by gently teasing off the seed.
Once the seedlings have reached onion adolescence (approx 8cm (3 inches) tall with 3 leaves) they can be gently pricked out into the growing container. The container will need to be at least 25cm (10inches) deep and each onion will need about 8cm (3 inches) of space to grow. So, the wider the container the better. Make sure that the compost you use to fill the container is not too high in nitrogen as this will give you a lovely leafy display above ground and very little below ground and in the case of onions it’s what goes on below ground that counts. Make sure that that the young onions get plenty of light. If you are not growing in a greenhouse, then put the seedlings outside on warm sunny days to get maximum light benefit and to help harden them off. Use a large Bell cloche, poly lantern cloche or poly tunnel to help protect from wind and temperatures below 10˚c. Once you are happy that night time temperatures are well above 8˚C then the onions can stay out without protection.
Keep your onions well-watered and when the leaves start to yellow, bend the tops over and brush back the soil to help the onions ripen. Pull them up and leave to dry in the sun until, like Grandpa Haxnicks, the necks are dry and the skin is papery (his joke, not mine!). Store in a cool, dry, frost free place with plenty of air circulation. Jute veg sacks are great for this.