So there's not much going on at this time of year, but one thing I tried last year (with some success) was growing onions from seed over winter in the greenhouse. Even though they grow slowly by spring they're well ahead of onion sets. So this year I've quadrupled the number and let's see what happens! 

The variety I've chosen is Ailsa Craig, which I've found is an ideal onion for our climate in Redbourn. Originally grown in Scotland and named after the island famous for producing the granite used in curling stones, the onion has a mild taste, matures between July and September and keeps well. 

I've sowed the onion seed thinly into plugged seed trays and will thin the seedlings down to one onion per plug, so hopefully we have around 100 plants come spring! Place the trays in a light position as this will help germination, but keep them out of direct sunlight as this can dry them out. It's important to keep the compost moist but not wet and water occasionally once the seeds sprout. The seedlings will survive frost in the winter, but in extreme cold weather don't over water as this could freeze or lead to mildew.