Techniques
Overwintering
Keeping a plant alive through winter, outdoors with protection or under cover, so it crops earlier or survives to the next year.
What overwintering means
Overwintering simply means getting a plant safely through the British winter, either left outside with some protection or moved somewhere sheltered. It splits into two quite different jobs. The first is encouraging tough, hardy crops to sit out the cold so they get a head start and crop earlier the following year. The second is keeping tender plants — ones a UK frost would kill — alive until the warmth returns.
Knowing which plant needs which approach is the whole skill. It comes down to a plant's hardiness: how much cold it can take before it suffers.
Hardy crops you overwinter outdoors
Plenty of crops are happy to spend winter in the ground and reward you with an early harvest. Garlic is the classic — plant cloves in October or November, let the cold trigger the bulbs to split, and lift them the following summer. Autumn-planting onion sets and broad beans (the variety 'Aquadulce Claudia' is the usual UK choice) work the same way: sown in autumn, they establish over winter and crop weeks ahead of a spring sowing.
These plants don't need cosseting, but a little help goes a long way. A mulch over the roots, a layer of straw, or a cloche on the worst-hit beds keeps off the harshest frost and stops winter rain rotting young plants. In milder parts of the south and west you can be more relaxed; in the colder north and east, more protection pays off.
Tender plants you bring under cover
The other half of overwintering is rescue work. Chilli and pepper plants are short-lived perennials, not annuals, so a healthy plant can be cut back, potted up and kept on a bright, frost-free windowsill or in a heated greenhouse over winter — giving you a flying start and earlier fruit next year. Mediterranean herbs like rosemary, bay and tender sages dislike cold, soggy soil; in containers they're easily moved into a porch, cold frame or unheated greenhouse for shelter.
The enemy in a UK winter is rarely just cold — it's cold plus wet. Damp, waterlogged compost rots roots faster than frost ever does, so keep overwintering pots on the dry side and raise them on pot feet so they drain freely.
Getting it right in the UK
Timing matters. Plant your hardy autumn crops while the soil still holds a little warmth (September to November), and move tender plants under cover before the first hard frost, usually from late October. Don't coddle the hardy ones — they actually need the cold — and don't gamble with the tender ones, which won't survive a single sharp night outdoors.
For more on stretching your harvests across the colder months, see our guide to year-round growing.
In a UK garden
In the UK, overwintering covers two jobs at once — getting hardy crops like garlic and autumn onions through a damp, frosty winter to crop early, and bringing tender plants such as chillies indoors so the cold doesn't kill them.
Example
Plant garlic cloves in October, leave them outside through the winter, and they sit quietly in the cold ground before romping away in spring for a midsummer harvest.