Planting Garlic and Onions for Overwintering: Get Ahead for Next Year

🌱 GrowMore CookMore App

Know what to sow, when to harvest, and discover recipes for your garden produce.

Planting garlic and onions in autumn for overwintering. This is one of my favourite jobs of the year, and I’ll tell you why — it’s the closest thing to time travel in gardening. You stick cloves and sets in the ground now, in October or November, and then basically forget about them for months. They sit through the worst of winter doing their thing underground while you’re inside eating soup and watching telly. Then spring arrives, everything starts growing, and you’ve got crops that are weeks ahead of anything you plant in spring. It’s like cheating, except it’s totally legal and nobody gets hurt.

I plant all my garlic in autumn now. Every single clove. Spring planting works too, but autumn-planted garlic consistently produces bigger, better bulbs for me. The cold winter triggers a process called vernalisation which is a fancy word for “the cold makes it grow better.” The cloves develop roots through winter, then when spring warmth arrives, they absolutely take off. By the time spring-planted garlic is just getting started, my autumn-planted stuff is already a foot tall with strong roots established. Game over. Autumn wins.

Same with overwintering onion sets. These are specific varieties bred to handle winter conditions — you can’t just shove any old onion set in the ground in October and expect it to survive. The overwintering varieties are tougher and will come through frost, rain, and everything else the British winter throws at them. And the reward is onions ready in June — a good two months before spring-planted ones. June onions! While everyone else is waiting until August. That’s the kind of smug satisfaction that keeps me going through the dark months.

Choosing Your Garlic

Always buy proper seed garlic from a garden supplier, not supermarket garlic. Supermarket garlic is often grown abroad in warmer climates and may carry diseases. Plus it might not be suited to our growing conditions. Seed garlic is certified disease-free and bred for UK conditions. It’s a few quid more but absolutely worth it.

There are two main types — softneck and hardneck. Softneck varieties like ‘Solent Wight’ and ‘Picardy Wight’ are the best for long storage and can be plaited. Hardneck varieties like ‘Lautrec Wight’ and ‘Music’ produce bigger cloves, have more complex flavours, and throw up a curly flower stalk called a scape in spring (which is edible and delicious). I grow both — softneck for keeping and hardneck for eating fresh.

Break the bulb into individual cloves just before planting. Use the biggest, healthiest cloves from the outside of the bulb — these produce the biggest bulbs next year. The little ones in the centre can be used for cooking or planted if you want but they’ll give you smaller bulbs. I save the six or eight best cloves from my biggest bulbs each year for replanting. It’s self-selection in action — every year the bulbs get slightly better because I’m only replanting the best genetics.

Planting Garlic

Dead simple. Make holes about 5cm deep, 15cm apart, in rows about 30cm apart. Drop a clove in each hole, pointy end up, flat (root) end down. Cover with soil and firm gently. That’s it. I use a dibber to make the holes — saves bending down and poking around with your fingers in cold soil. My knees are not what they were.

Don’t push the cloves in with force — this compacts the soil underneath and can hinder root development. Just pop them in gently. If your soil is heavy clay, add a bit of grit to the bottom of each hole for drainage. Garlic sitting in waterlogged soil over winter will rot. Ask Ronny — he lost a whole bed of garlic one winter because his clay soil turned into a swamp. Now he grows his in raised beds with loads of grit mixed in. No more problems.

I plant about fifty cloves every autumn. Sounds like a lot but garlic stores for months, we use it in everything, and I save the best for replanting. Between us, that’s about a year’s supply of garlic. Self-sufficiency in garlic is a very achievable goal and one of the most satisfying things in the kitchen garden. Never buying garlic again. What a feeling.

Overwintering Onion Sets

Overwintering onion sets work slightly differently to garlic. You’re planting small bulbs (sets) rather than individual cloves. The varieties bred for autumn planting include ‘Radar’, ‘Shakespeare’, ‘Senshyu Yellow’, and ‘Troy’. These are all bred to be cold-hardy and resistant to bolting (running to seed instead of bulbing up, which is the main risk with overwintering onions).

Plant them in October or November, about 10cm apart in rows 25-30cm apart. Push them into the soil so just the tip is showing. Firm the soil around them. That’s it. Even easier than garlic. I can plant a whole bed of onion sets in about twenty minutes while listening to a podcast. Multi-tasking at its finest.

The sets will develop small roots and maybe a bit of green shoot before winter. Then they’ll basically stop growing and sit tight through the cold months. As soon as the soil warms in spring, they’ll take off. By June or early July you should have decent-sized onions ready to harvest — way ahead of spring-planted ones which won’t be ready until August or September.

Through the Winter — What to Expect

Once planted, there’s very little to do through winter. The garlic and onions are basically on autopilot. You might see some green shoots appearing, especially during mild spells — that’s perfectly normal. Don’t worry about them. They’re fine. A bit of frost burn on the leaf tips is nothing to panic about either — the growing point is underground and protected.

The main thing to watch for is waterlogging. If your soil stays very wet for prolonged periods, the bulbs can rot. If you know your soil is prone to winter waterlogging, consider raising the bed slightly or improving drainage before planting. Heavy clay soils are the worst for this — add grit or sharp sand to improve things.

Weeding should be minimal through winter, but do keep an eye on it. A few weeds around your garlic and onions isn’t the end of the world, but a thick carpet of chickweed competing for nutrients isn’t ideal. A quick hoe on a dry day every few weeks through winter keeps things under control. Good mulching with straw or leaf mould around the plants suppresses weeds too and provides a bit of insulation.

Spring Onwards

Come spring, things get exciting. The garlic will put on rapid growth as the soil warms — strong green leaves shooting up, getting taller every week. Feed with a general-purpose fertiliser or liquid seaweed in March to give them a boost. Keep watering in dry spells through spring and into early summer.

Hardneck garlic will produce scapes in late spring — those curly flower stalks. Cut these off (they’re trying to flower which takes energy away from bulb development). But don’t waste them — garlic scapes are a delicacy. Chop and use like spring onions, make pesto from them, or stir-fry them. They’re delicious. Free bonus crop from your garlic. Can’t beat that.

Overwintering onions should be bulbing up nicely by May and ready to harvest from late June. Harvest when the tops start to yellow and flop over. Cure them in the sun for a couple of weeks (or under cover if it’s wet) and they’ll store for months. Early onions from overwintering sets, plus main crop onions from spring planting — that’s nearly a full year’s supply of onions right there.

Look after yourselves. Take good care. 🌱