Onions and Garlic
Onions and garlic are satisfying to grow and not difficult even for a beginner. Follow our guide to get the best results and furnish yourself with a year-round supply.
Various types of onion, including spring onions, pickling onion and shallots can be successfully grown from sets or from seed, some from both.
Onion sets are small, immature onions, planted in spring or late summer. The sets increase in size and each forms one full-sized bulb when ready to harvest. Where possible, choose onion sets that have been heat-treated. This means their flower embryos have been killed, so they’re less likely to run to seed or bolt. Generally, growing onions from sets is easier and more reliable than from seed and in cooler, damper areas, the sets should give a better yield of larger bulbs than if grown from seed. However the range of varieties available is far greater if growing onions from seed.
What to do
- A sunny, well-drained site is essential for growing good crops of onion and garlic. It’s possible to grow good onions on heavy soil, but the drainage should be improved prior to planting with grit and bulky organic matter, and the cloves planted in ridges of soil 10cm (4in) high to help reduce soil moisture.
- Onions and garlic both like fertile soil, but neither require much nitrogen and so shouldn’t be grown on freshly manured soil. Instead, dig over and manure the ground several months before planting. If the soil is acid it’s worth liming it so its pH level becomes neutral or even slightly alkaline.
How to sow seed
- Sow seed in modules in January or February at 10-15°C (50-59°F).
- Sow five or six seeds per module in damp seed compost – when planted out the clumps of bulbs will push themselves apart as they expand.
- Cover seeds with a layer of vermiculite and label with variety name and date of sowing.
- To have a year-round supply, you can sow once in spring for harvesting from August, and again in late summer or autumn to be ready from June, although a second planting isn’t recommended in very heavy, wet soils. Onions should be given as long a growing season as possible to reach maximum size.
Growing onions from sets
- The easiest way to grow onions is from sets, available from garden centres.
- Prepare the soil a couple of months before planting by digging over and adding manure.
- Plant the sets in spring in shallow drills and cover them so the necks are just protruding from the soil.
- Weed regularly and water sparingly.
Harvest as soon as the foliage starts to yellow.