What to plant in September in England is mainly crops for winter and early spring: the RHS suggests sowing overwintering spinach, winter lettuce, rocket and salad leaves, and planting overwintering onion sets and spring cabbages. It is also a busy harvest month, so most of the bed is still full of summer crops while the first autumn sowings go in.

Illustration of a late-summer raised bed with staked tomato plants carrying ripe fruit at the back and a freshly sown row of small spinach seedlings at the front
IllustrationSeptember: summer crops are still cropping while the first winter sowings, such as spinach, go into the gaps.

This page sets out the RHS and Gardeners' World advice for the month, then what Sowstory plans: in a Sowstory plan, annual spinach is the only crop that starts in the bed in September.

At a glance: what to plant in September

TaskCropsSource
Sow under coverNothing essential this monthRHS
Sow outdoorsOverwintering spinach, winter lettuce, rocket, salad leaves, hardy spring onions; green manuresRHS
Plant outdoorsOverwintering onion sets; spring cabbages sown in July or AugustRHS
HarvestTomatoes, beans, courgettes, cucumbers, maincrop potatoes, beetroot, calabrese, the first kale and Brussels sproutsSowstory harvest windows

For the whole year on one page, see the vegetable sowing calendar for England.

Sow indoors

The RHS September list has no indoor sowings: everything on it goes straight into the bed. Sowing under cover picks up again next month, when Gardeners' World suggests early-summer cauliflower in trays, and in November, when the RHS suggests broad beans in pots in an unheated greenhouse for colder areas.

Sow or plant outdoors

Spinach, winter lettuce, rocket and salad leaves

These are the core September sowings on the RHS list, all aimed at picking through autumn and into winter. Sow them in the gaps left by summer crops as you clear them. Spinach and lettuce are among the leafy crops that tolerate a bed with four to six hours of sun, which helps as days shorten. Our guide on how to grow lettuce covers sowing depth and picking.

Spring onions for next spring

The RHS says hardy spring onion varieties sown in late summer or early autumn crop from March. Sowstory's spring onion profile is sown from March to August, so a September sowing is outside the app's plan.

Overwintering onion sets (RHS advice)

The RHS lists overwintering onion sets for September, protected from birds until they have rooted. Gardeners' World gives September to November for planting them, 10–15 cm apart in rows 30 cm apart. Avoid heavy soil that stays waterlogged in winter, where the RHS says sets may rot. Sowstory's onion profile is spring-planted sets, started in March or April; see how to grow onions for both routes.

Spring cabbages

Plant out spring cabbages that you sowed in July or August, as the RHS suggests.

Green manures

For a bed you will leave empty over winter, the RHS suggests green manures such as winter tares and Italian ryegrass. In a no-dig bed, it suggests covering the green manure with cardboard six to eight weeks before you want to plant.

In a Sowstory plan this month

In September, annual spinach is the only crop profile Sowstory starts in the bed. Its window also covers spring and August, and September is the last month of it. When spinach is in your plan:

  • Spacing: Sowstory allows 30 cm between rows and 15 cm between plants, with up to three rows.
  • How many fit: three rows along a 1.2 × 2.4 m bed come to about 48 plants as a simple estimate. The plant spacing chart lists other crops.
  • Sun: it tolerates four to six hours of direct sun.
  • Time in the bed: Sowstory reserves the space for about 10 weeks (70 days).

The quick crops that Sowstory starts in August, such as radish, lettuce, rocket, baby turnips and pak choi, are not started in September. Garlic takes over from October.

Meanwhile much of a summer bed is still cropping. Sowstory's harvest windows for tomatoes, runner and climbing French beans, cucumbers, courgettes and maincrop potatoes run into October, and curly kale, standard kale and Brussels sprouts all start in September.

If you want to plan what follows each summer crop as it comes out, Sowstory lays out your bed to scale and gives a month-by-month plan, including succession where supported. It is coming soon to the App Store, and your first bed plan is free.

Sowstory's months are England-wide and not adjusted to your postcode, and the app gives no frost date for your address, so judge sowing conditions in your own garden.

Jobs this month

From the RHS September list:

  • Lift potatoes. Sowstory's maincrop potato harvest window runs from August to October.
  • Cut down asparagus once the foliage has browned, and mulch the bed.
  • Protect new onion sets from birds until they root.
  • Clear finished crops to make room for winter sowings or a green manure.

First frosts

Air frost is rare in September across most of England, but not everywhere. Met Office averages for 1991–2020 give Shap, in upland Cumbria, about half a day of air frost in September, rising to nearly four in October. Ground frost can come before air frost, and the Met Office says it is possible on a clear, calm night when the air is forecast to drop to 0–4°C. Tender crops such as tomatoes, beans and basil are damaged by frost, so keep an eye on the forecast late in the month in cold, high or rural gardens. Our frost dates guide explains the difference between ground and air frost.

What not to sow yet

  • Garlic. The RHS puts the main planting season in mid-autumn to early winter, and Sowstory's window opens in October.
  • Overwintering broad beans and hardy peas. The RHS lists these from October, in mild areas.
  • Tender crops for next year. The RHS starts tomatoes, chillies and cucumbers in a greenhouse from mid-February.

Last month's list is in what to plant in August; next month, see what to plant in October, when garlic planting begins.

Sources