What to Plant in Autumn in Scotland: Garlic, Overwintering Onions, Broad Beans and Peas

The autumn planting window is short: it opens in late September and is mostly shut by mid-November. Garlic cloves and onion setsSmall immature bulbs planted directly rather than grown from seed, giving a faster, more reliable crop in a short growing season. Full definition → go in over a matter of weeks, not months: too early and they run up top growth that the first hard frosts and winter gales will strip, too late and they sit in cold, wet ground without a root to hold them, which is when they lift, rot or simply sulk. Only some of the usual autumn crops earn the risk in a Scottish garden.

The calendar: how short the window really is

The number that matters is the average air-frost days a month (days when the air temperature falls below freezing). October is the hinge, and the gap between coast and hill is wide. The full regional table is on Scottish frost dates, with lowland and upland figures for each region.

The windows below shift by region and by altitude. Our reading of that frost data: in a lowland Central Belt, Borders or east-coast garden, the practical autumn planting window runs from late September to about the end of October for onion sets and shallots, into early November for garlic and broad beans, and closes sooner on higher ground, where frost arrives earlier (Braemar averages 5.7 air-frost days in October). On the milder west coast and islands it stretches a little into early November. Local frost pocketsA low-lying spot where cold air drains and pools on still nights, making it noticeably more frost-prone than the surrounding area. Full definition → can override any of this by weeks.

Late planting is punished by cold, wet soil more than by frost, and planting too early and warm lets onion sets in particular push out leaf that winter then strips. For late-summer sowings that are a different job, see the top five crops for a late second sowing.

The crops at a glance

Depth and spacing at a glance

Garlic: the one that belongs in autumn

Garlic needs one to two months at 0 to 10°C to form a bulb. A Scottish winter supplies that without effort, which is why autumn planting suits garlic better than almost any other crop in the ground. Plant from mid-autumn to early winter: in most Scottish gardens, October into early November. Hard frost is not the risk, cold, standing water is. Garlic also dislikes acid soil, and many Scottish soils are naturally acidic, so test the bed (soil pH testing and adjustment explains how) and lime in autumn if it needs it.

Plant each clove pointed end up with the tip 2.5cm below the surface (spacing is in the table above). On light or free-draining ground, deeper planting can give bigger bulbs. On heavy ground, keep it shallow, because deep cloves in wet clay rot. Work in two bucketfuls of well-rotted manure or compost per square metre beforehand to improve structure and drainage. The full method is in the garlic growing guide.

Hardneck or softneck

Hardnecks carry fewer, larger cloves, taste stronger, and are more prone to bolting; they store four to six months. Softnecks pack in smaller cloves, are unlikely to bolt, and can store for up to a year if planted in autumn. On winter hardiness, hardnecks are generally hardier and able to grow throughout the UK, while softnecks are less tolerant of prolonged cold. In a cold, upland or frosty inland garden, lean towards hardneck, and in a mild, wet, coastal garden either type is workable if the drainage is right. Named varieties are compared in the best garlic varieties for Scotland, and what to do with the crop afterwards is in storing onions, garlic and shallots.

When the soil is wet

Wet soil makes garlic more prone to disease, and autumn planting is the worst time for it. A quick check: after heavy rain, dig a spade-deep hole, and if water is still standing in it next day, treat the bed as wet and use ridges or modulesA tray divided into small individual cells, each sown with its own seed or seedling, so each plant grows undisturbed roots until it's ready to plant out. Full definition →. There are two practical answers. The first is to start the cloves in modules (cell trays or small pots, one clove each) in autumn and plant them out in spring, growing them on in a cold frame meanwhile, and cold frames in Scotland covers the set-up. The second is to plant on raised ridges of soil about 15cm high and 20cm wide, which keeps the clove above the worst of the winter water. If a plot floods rather than merely stays damp, fix the drainage first: see flooded plot drainage.

Birds will pull newly planted cloves and emerging shoots out of the soil, so lay fleece or netting over the bed until the roots have taken hold. In cold areas, cloches over winter help the roots. Keep garlic away from ground with a history of allium disease (onion white rot persists in soil for years) and watch for allium leaf miner and leek rust on the leaves later in the season.

Overwintering onions and shallots

Overwintering, or Japanese, onion sets can be planted in autumn and harvested in June and July, earlier than a spring-planted crop, which comes in from July to October. That is the whole appeal: an onion bed cleared before the summer sowings need the space. The catch is that this is a marginal crop in Scotland. Autumn planting should be avoided where the soil is heavy and prone to waterlogging in winter, because the sets are likely to rot.

Push each set in so the tip just shows (depth and spacing are in the table above); wider spacing gives larger bulbs. Birds peck newly planted sets out of the ground, so cover with biodegradable fleece or netting until they are rooted. The aim is to get sets in early enough to grow a few roots before the first hard frost but not so early that they make lush leaf, so late September to mid October in a lowland garden, earlier at altitude.

Rot in wet soil is the first failure, and a cloche does not cure it. Bolting is the second, and it is the reason to buy true overwintering (Japanese) types rather than ordinary spring sets: the overwintering types are less sensitive to the cold that would otherwise trigger flowering. Heat-treated sets are the spring-planting answer to the same problem, not an autumn one. Autumn-planted onions also keep less well than spring ones, lasting until early winter rather than into spring, so this crop is for eating fresh through summer, not for the store. If it goes wrong, the fallback is easy. Onion sets go in from spring, and the onion growing guide and best onion varieties for Scotland cover which types to choose.

Shallots follow the same logic. Sets can go in during autumn or even winter, and some varieties are less sensitive to cold. The same warning applies: avoid autumn and winter planting in heavy soil prone to waterlogging, because the bulbs are likely to rot. Where the ground is anything short of well drained, spring planting is the safer default; see the shallot growing guide and best shallot varieties for Scotland.

Broad beans: worth it in the right spot

Broad beans are the classic autumn sowing, and the reputation is deserved on the right site. Aquadulce Claudia holds the RHS AGMThe RHS's Award of Garden Merit: a UK-wide trials award for reliable performance, not a Scotland-specific recommendation. Full definition → and is a good variety for autumn sowing and overwintering. October to November sowing is possible in milder parts of the UK or very sheltered sites, especially those with well-drained soil. Mild is relative in Scotland, and not every garden is sheltered or free-draining.

Where it works: a lowland garden in the east or west, or a coastal plot with a windbreak, well-drained soil and no history of standing water. Depth and spacing are in the table above. Sow in October or November, aiming for late October in a lowland garden, so seedlings are up but not lanky by the time the hardest frosts arrive.

Where it does not: exposed hilltops and hill gardens, high-altitude sites, frost pockets, and any bed that waterlogs. Where the site and soil are too windy or wet for autumn-sown beans, a February indoor sowing is the alternative. Autumn seed sown outdoors may also be eaten by mice, and sowing under cover avoids that; for the local picture see mice and voles.

Young plants need shelter in cold spells: cloches or fleece help, and garden fleece grades and timing helps choose the weight. Protecting plants from frost covers the wider toolkit. Frost heave, the freeze-thaw lifting that pushes shallow roots out of the ground, can also set autumn beans back on cold, damp soil, and a firm, well-drained bed is the best defence.

In spring, pinching outRemoving the soft growing tip of a stem to stop upward growth and make the plant branch out sideways instead. Full definition → the shoot tips once the lowest flowers have set small pods redirects effort into pods and reduces pest pressure, blackfly especially (black bean aphid is the one to watch). Look out for broad bean rust in a damp summer. Varieties are compared in the best broad bean varieties for Scotland, and the full method is in the broad bean growing guide.

Broad beans do not need winter cold to flower, so leftover Aquadulce seed can be sown in spring. On an exposed or wet Scottish plot, a February sowing under cover or a March sowing outdoors beats an autumn sowing that loses half its plants. Yields fall away after mid-April, so spring should not drift too late.

Autumn peas: a gamble

The RHS lists autumn sowing as an option but only for plants kept in a greenhouse or cold frame over winter, for planting out in early spring. Gardeners' World says you can sow in autumn or late winter for peas ready from May onwards, but warns of losses from cold weather or mice, and suggests starting plants indoors in autumn to avoid seed being eaten.

In Scotland an outdoor autumn sowing of peas is a gamble, and mostly a losing one. Young pea plants sitting in cold, wet ground through a Scottish winter face rot, slugs, mice and hard frost, and even a survivor gains only a few weeks on a March or early April sowing, which is the timing on the pea growing guide. If you want to try, sow into modules (small cell trays or pots) in a cold frame or unheated greenhouse, keep mice off the trays, and plant out in early spring. Otherwise put the effort into a properly timed spring sowing and a succession, as in succession planting for beginners, and choose from the best pea varieties for Scotland. Pea moth is a summer matter and does not change the autumn verdict.

Scottish risks to plan for

Waterlogging is the risk that runs through garlic, onion sets, shallots and broad beans alike. It does not need a flood: soil that stays saturated for weeks in December is enough. Improve drainage with organic matter, use raised ridges or beds, or move the crop to modules under cover.

Slugs can stay active through a mild, damp winter, and newly emerged shoots are vulnerable (slugs). Mice will dig out large seeds, so broad beans and peas are the targets; cover the rows, set traps, or raise seedlings under cover. Hard frost heave pushes shallow-planted sets and cloves upward on freezing and thawing ground. Check beds after a thaw and press anything lifted back in. Short cold springs matter in the opposite way: autumn crops that survive still cannot run away in a cold, late April, so the head start over spring sowing is often smaller in Scotland than the June-versus-July figures suggest. Green manuresA fast-growing crop sown specifically to be dug back into the soil, adding organic matter and, with legumes, fixing nitrogen. Full definition → are the alternative for beds that will not be planted; see green manures for a short Scottish season.

When spring beats autumn

For a good number of Scottish gardens, spring wins for at least half this list. If the soil is heavy, spring onion sets, spring shallots and spring-sown beans are the safer default. If the garden is exposed or high, autumn broad beans are not worth the seed. Garlic is the exception: it is also the crop most tolerant of a slightly late start, provided the cloves are in before the ground is frozen solid, and heavy-ground gardeners can still have it by starting cloves in modules. For crops you can still sow under cover through winter, see winter salads under cover and top five crops for winter harvest.

Common questions

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