- Brassicas, beet, tomatoes and lettuce benefit from the masking effect of the smell of onions;
- Onions and leeks are supposed to deter carrot fly;
- Strawberries are apparently less vulnerable to disease alongside onions;
- Onions benefit from weed cover when they are ripeneing - the weeds absorb water and excess nutrients (especially nitrogen).
Onions grown from sets mature more quickly, are less prone to disease and onion-fly, and easier to grow than onions from seed. I have had no problem with them bolting.
- Choose a variety which keeps well - it is in storage that you will have most problems.
- Plant out the sets about 4 inches apart, in rows 10-12 inches apart, from mid-March to mid-April. Push them gently into the ground - avoid damaging the basal plate from which the roots will grow. Firm the soil around them so that only the tip is showing.
- Birds may think long tops on your sets are straw - great for nest building, but not so good for you to have your sets strewn around the plot. Cut off the tops about a half inch above the bulb. Also string some twine along and across your bed.
- Your sets may arrive too early for you to plant. Open the package and lay out the sets in a cool (but frost-free), well-lit place to prevent them sprouting.
- Keep the onions weed-free, water them in early stages if the weather is dry, break off any flower stems which may appear.
- Once the onions have swollen, stop watering, and pull back the soil a little to let them ripen in the sun.
- The onions will be ready for harvest about 2 weeks after the leaves yellow and topple. Lift them gently.
- Before storing your crop, let the onions dry for anything up to three weeks. I do it indoors - there are no vandals, and it won't rain inside!
- Check them over carefully and put the healthy ones into old pairs of tights, to hang in a cool well-lit place.
- Onions which are not in perfect condition rot in store - and spread the rot to all the others. You do NOT want to store onions which are
- thick necked,
- spotted - neck rot shows itself as grey mould, with black spores under the skin of the onion around the neck
My main-crop onions usually last through to the next crop - I have "had to" make several jars of chutney some years. But you can have an earlier crop of good-sized onions by planting sets in late September or October, 7 or 8 inches apart each way; they survive winter well, and will be ready for use in June. They do not store so well, but can fill a gap between crops.
I have also grown Pickling Onions from seed - it's very straightforward, sowing rows of seed thinly enough so you don't need to thin them. Otherwise, look after them just as you would the onions from sets.
Varieties I've tried.
Onion sets - ready August
Gives me a reliably good crop of large flat bulbs, with good flavour; they keep very well.
Onion sets - ready August
Good crop of round bulbs, with good flavour; they kept very well in 2000 and 2001, but not 2002.
Onion sets - ready August-Sept
Vandalised - no crop.
Brown Pickling Onions
Seed - gives small onion, for pickling(!)
Very reliable, good size for largish pickled onions.
Growing Calendar - Onion
Timings are based on my allotment in Yorkshire; southerners will start earlier, northerners even later!
Onions (seed and pickling varieties
Onions (from sets) - maincrop
Onions (from sets) - Japanese or overwintering