There’s just about time to plant onion sets if you get them planted in the next few weeks. Sets, for those not in the know are small immature onions where development has been stopped and which will grow as soon as planted. Why use sets not seed? Sets are quicker to get going, more resilient than seedlings to pests and diseases and easier than raising from seed. The only down side is that there is less choice of variety in sets than seed. There are two different sorts of onion set: ordinary, fairly inexpensive sets and the more expensive heat treated sets. The benefit of heat treated sets is that they will not ‘bolt’ ie flower and go to seed, which spoils the keeping qualities of the onion. These treated onions have been kept at a high temperature for long enough to kill the embryonic flower and so prevents bolting. The heat treatment doesn’t however protect the onion against disease, the treatment is solely to stop bolting. In hot dry summers it’s probably worth the extra cost of the heat treatment. You can expect to pay around from £1.50 for 25 sets to £4 for 75 set packs of untreated onions and about £4.50/£5 for smaller packs of heat treated sets. Good varieties to buy are: Setton, Sturon, Hercules, Red Ray and Electric Red. While you’re looking at onions don’t be tempted to buy garlic though, it’s too late now, as garlic needs some really cold weather during its development or it doesn’t form into cloves and you’ll end up with a single bulb like an onion.