When to plant garlic

Autumn is the main planting season. In Germany, Austria and Switzerland, plant from late September to the end of October; in mild areas you can keep going into November as long as the ground isn't frozen. In the UK, October and November are the usual months, and December still works in mild gardens.

Autumn planting gives the biggest bulbs for a simple reason: garlic needs a spell of cold, roughly four to eight weeks at 32–50°F, before it splits into cloves. Cloves planted in autumn root before winter and get that cold for free. Without it, you often lift a single round bulb instead of a head of cloves.

If you missed autumn, plant in February or March as soon as the soil can be worked. The cloves still catch some cold, but expect smaller bulbs. Softneck and spring-type varieties cope best with a spring start.

Start with seed garlic from a garden supplier or regional organic garlic. Supermarket bulbs are usually softneck varieties bred for warmer climates, may be treated to stop sprouting, and can carry viruses, nematodes or white rot, which then stays in your soil for many years.

Choose a sunny spot with free-draining, humus-rich soil. Garlic rots in waterlogged ground, so on heavy or wet soil a raised bed is the safer choice. Aim for a pH of about 6.5–7; anything from 6 to 7.5 is fine. Work in compost before planting.

Break the bulb into cloves just before planting and use the largest ones. Push each clove in upright, pointed end up, so its base sits about 2 in deep and the tip has 0.8–1.2 in of soil over it. Plant a little deeper in light, sandy soil and cold areas with little snow, and a little shallower in heavy clay.

Space cloves 6 in apart in rows 10–12 in apart. A 120 × 80 cm raised bed then holds three rows of eight, 24 cloves. In a rich bed you can go down to 8 in between rows and fit 32, but closer planting keeps the leaves damp and makes rust more likely.

Garlic is hardy in Central European and UK winters. A trial at the Bavarian vegetable trial station in Bamberg overwintered seven of eight autumn-planted varieties without trouble. In cold spells without snow, a 2–3 in mulch of straw or leaves protects the young shoots.

Garlic competes poorly with weeds, so keep the bed clean, ideally by hand so you don't nick the shallow roots. Water only in dry spells from March to June, and then deeply rather than often.

Give a light organic feed in early spring, around March or April, and no nitrogen after May. Too much nitrogen late in the season shortens storage life and, together with a lack of potassium, encourages rust.

Hardneck varieties send up a curling flower stalk, the scape, in early summer. Cut it off once it curls so the plant puts its energy into the bulb. Scapes are tender and mild, good in a stir-fry or pesto.

Autumn-planted garlic is usually ready from late June into July, about eight to nine months after planting; spring-planted garlic follows in July or August. Stop watering two to three weeks before, when the lower leaves start to yellow.

Lift the bulbs when the lower third to half of the leaves have turned brown while the top ones are still green. Don't wait until the whole plant has died back: the bulbs then start to split open and don't keep as well. Loosen the soil with a fork rather than pulling on the stems.

Leave leaves and roots on and dry the bulbs in a single layer, or hung in bunches, somewhere shaded, dry and airy for two to four weeks, keeping them below 86°F. They are ready when the necks are dry and the skins papery. Then trim the roots, cut the stems back to 0.8–1.2 in, or braid softneck garlic.

Store garlic cool, dry, dark and airy, in a net, basket or braid rather than the fridge. Hardneck garlic keeps for about four to six months, softneck for six months to a year.

Hardneck garlic grows a stiff central stalk with a scape. It forms fewer, bigger cloves with a stronger flavour, is generally the more cold-hardy type, and keeps for about four to six months.

Softneck garlic has no stiff stalk. It makes many smaller cloves, stores the longest and can be braided, but is less reliably hardy in cold winters. Almost all supermarket garlic is softneck.

Rust shows as orange pustules on the leaves, most often in humid weather, in crowded beds and on plants given lots of nitrogen but little potassium. Space generously, feed in balance and clear away old leaves.

White rot is the one to fear: leaves yellow and wilt, and the base of the bulb grows white fungus with tiny black resting bodies. Those survive in soil for at least 15 years, so no rotation can clean an infected bed. Keep it out with healthy planting stock, and don't carry soil between beds on tools or boots. Never plant alliums where it has appeared.

Leek moth caterpillars and allium leaf miner larvae tunnel into the leaves. The leaf miner flies in March–April and again in September–November, so freshly planted autumn garlic can be hit. Fine insect mesh with holes of about 0.8 mm keeps both out.

Garlic belongs to the onion family with onions, leeks, shallots and chives. Leave at least four years before any of them grows in the same bed again.

Planting tables often pair garlic with strawberries, carrots, beetroot or tomatoes and keep it away from beans and peas. We found no solid evidence for any of these pairings with garlic itself; they are tradition. Mixing carrots with alliums is harmless and might confuse carrot fly, but the research behind that was on onions, not garlic.

The one rule with a real reason: don't grow garlic next to or straight after other onion-family crops, because they share pests and diseases.