Summer Sowing Onions
August is the time to make a sowing of onions to give you a crop in mid-summer next year. You can sow them direct, into seed trays or into modules.
Let’s start with direct sowing: the advantage is that you are planting in soil that has naturally warmed up over the summer, they settle well and they are ready to tolerate cold winters. Prepare the soil by digging and raking it to a fine texture. Avoid sowing into very wet soil. Sow thinly into rows at a depth of 1-2cm. The rows can be 15-30cm apart from each other. As the seedlings start to grow they will need to be thinned every now and then to create space for bulbs to develop. Don’t waste the seedlings you take out – these can be used g as you would chives. Once you reach a spacing of about 15cm you’ll no longer need to thin them. This is a good method if you are sowing large numbers of the same variety and don’t mind sacrificing plenty when thinning.
Method 2 is sowing in a flat seed tray: sprinkle the seeds on to damp compost and then cover with 1cm deep of more compost. Once the seeds have germinated and are about 1cm tall and at ‘crookneck’ stage (the seedling is still bent over, with both the root and tip in the compost), they should be pricked out into trays at a spacing of about 5cm. They need to have 2-3 leaves before transplanting to about 15cm apart in rows in October. If we are trying to grow the biggest onions we use this method but there is no escaping that this it is time consuming.
Method 3 is sowing in modules: the easiest and least time consuming way. Sow 4-6 seeds per module into damp compost and cover with about 1cm more compost. Once they are straightening up simply plant each clump into the ground. Space the clumps about 20-25cm apart each way and the onions will simply push themselves apart as the bulbs begin to swell in the spring. I am not handing out prizes for you guessing that we sow most of our onions this way, it’s a good compromise when you struggle to find enough time but in our experience the individual onions won’t be quite as big as they can be when using either of the other two methods.
Some general onion information: onions love a sunny, open position. Traditionally sandy beds have been favoured due to their free-draining nature but any fertile ground with good drainage is fine. Seeds will germinate within about three weeks. You will need to keep on top of the weeding as onions do not like competition and if you like using a hoe then making sure your row spacing is the right size to fit you hoe will save you a lot of frustration come spring time! In spring, you can boost post-winter growth by apply a seaweed based feed.
Drying your onions: don’t be tempted to rush this if you want to store your crop. Your onions need three weeks in a light and dry place. If the weather is fair we lay ours out on the path but after a day or two of laying them out and picking them up it can become a chore. We have found putting them in shallow boxes makes it much quicker to rescue them from a rain shower or to put them in the porch. Boxes are readily available & they also protect against knocks and catch all the stuff that falls off whilst drying. Of course if you are going to freeze your onions you don’t need to dry them: simply peel, slice or dice and bag up – it couldn’t be easier.
Hope this all helps you to have a super onion crop.