BOXING CLEVER WITH ONIONS
Traditionally sown on Boxing Day, onions can be started off through the winter and Paul has a few tricks that guarantee you a bumper crop.
The alliums; onions, garlic, shallots, chives, and a wonderous array of new, non-aromatic, hybrids for the flower garden, are possibly the most useful plants known to man. They share two really important properties, apart from the wonderful flavours. They use sulphurous alkenes as a defence mechanism against infection – we can make use of this too, and they store masses of sugar in swollen leaves (in the case of a bulb) or swollen stem (in the case of a corm, like garlic).
Once they have been thinned, keep them warm for another week and then put them into a greenhouse where the temperature is about 15C (60F). These are then ready to transplant about May time. You can put some black plastic over the well dug and hoed ground to warm it. Plant at about 15cm (6in) apart, with rows 30cm (12in) apart.
I never have any problems with ‘Ailsa Craig’ but try ‘Macro’ and for a red onion, try ‘Red Baron’. ‘Long Red Florence’ is a great pickier – even though it is a funny shape.
Sow on the shortest day and harvest on the longest day, this has been the motto – especially for shallots, and most of the books say a room temperature of 15C (60F). Generally speaking, exhibitors sow at a much warmer 18-21C (65-70F), in trays, indoors.
The idea is to keep the seedlings warm, well ventilated and transplant them to their growing positions in soil that has had a chance to warm up. This means you can start your onions as early as November and have them in the tunnel bed in late January, where they will bulb up for late spring. Alternatively you can kick them off in January/February and have really decent specimens for planting out not much later in spring too.
The reason for sowing as early as you can is that onion size is directly related to the number of leaves it produces. The more leaves the better the onion. Show onions are huge and have a reputation for having poor flavour. However, choosing the right variety, you can have good sized onions – not big enough to break any world records – that are simply great to eat.
Sow in trays, liberally, in good quality compost and do everything you can to stop them from becoming chilled. Water gently, don’t get the seedlings wet, and water sparingly, otherwise you will get damping off.
As they grow, thin the onions to 2cm (1/4 in) apart and let them grow – leave them alone. Simply add a little fertiliser to the water every now and again. Although they are packed with antibacterial chemicals they are prone to damping off, a fungal problem.