What To Plant In September UK
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In September in the UK, sow winter salads, spinach, spring onions, overwintering onions, broad beans in mild areas and green manures outdoors. Start lettuce, herbs, oriental leaves and microgreens under cover. Plant spring cabbage, hardy salads, overwintering onion sets and garlic later in the month.
September is a month of transitions in the UK vegetable garden — summer crops winding down, overwintering ones going in, and the soil still warm enough to make late sowings worthwhile.
September is a transition month: harvest summer crops, protect late crops, clear finished beds and start planning autumn and winter cover. Use the UK Vegetable Garden Planner PDF to record what grew where before the season fades from memory.
September Planting Preview
September Planting Quick Table
| Job | Good September options | Notes |
|---|---|---|
| Sow outdoors | Winter salads, spinach, spring onions, overwintering onions, broad beans in mild areas and green manures. | Keep seed beds moist and protect young salads from slugs and cold snaps. |
| Start under cover | Lettuce, herbs, oriental leaves and microgreens. | Use modules, trays, windowsills, cold frames or a greenhouse for more reliable germination. |
| Plant out | Spring cabbage, hardy salads, overwintering onion sets and garlic later in the month. | Do not plant garlic or onions into waterlogged soil. |
| Harvest now | Tomatoes, beans, courgettes, potatoes, carrots, beetroot, late salads and herbs. | Check tender crops before nights get colder. |
September Garden Jobs
- Clear finished crops and compost healthy plant material.
- Protect late harvests from cold nights and wet weather.
- Sow green manure where beds will otherwise sit empty.
- Plant overwintering onions in suitable, free-draining soil.
- Record crop rotation notes before clearing beds.
- Check courgettes, squash and cucumbers for powdery mildew.
What To Harvest In September
September harvests can include tomatoes, beans, courgettes, potatoes, carrots, beetroot, late salads and herbs. Lift potatoes when plants are ready, keep picking beans while pods are usable, and bring tender crops under control before colder nights slow growth.
Common September Mistakes
- Leaving tender crops outside too long without watching night temperatures.
- Delaying overwintering onions until soil is too wet or cold.
- Leaving cleared beds empty instead of sowing green manure or planning cover.
- Forgetting to record what grew where for crop rotation.
- Ignoring powdery mildew on tired courgettes, squash, cucumbers and peas.
Useful September Links
- UK vegetable planting calendar
- What to plant in August UK
- What to plant in October UK
- When to harvest potatoes UK
- Powdery mildew treatment UK
- UK Vegetable Garden Planner PDF
Frequently Asked Questions
What vegetables can I plant in September in the UK?
In September, UK gardeners can sow winter salads, spinach, spring onions, overwintering onions, broad beans in mild areas and green manures. You can also plant spring cabbage, hardy salads, onion sets and garlic later in the month.
Can I plant onions in September?
Yes. RHS guidance confirms overwintering onion sets are commonly planted in autumn, including September in suitable conditions, so they can establish before winter.
Can I sow spinach in September?
Yes. Spinach can be sown in September for autumn and overwintering crops, especially with protection in colder areas.
Can I sow broad beans in September?
Broad beans are usually more common from October or November, but September can work in mild areas if the soil is suitable and plants do not become too soft before winter.
What should I harvest in September?
Harvest tomatoes, beans, courgettes, potatoes, carrots, beetroot, late salads and herbs. Keep an eye on tender crops as nights become cooler.
Should I sow green manure in September?
Yes, September is a useful time to sow green manure on empty beds so soil is covered through autumn and winter.
Plan your September beds
Turn this month's list into a layout: sketch your plot in the free Garden Layout Planner, then follow the whole season with the UK Vegetable Garden Planner (printable PDF, 80 pages). For the full year, see the UK vegetable planting calendar, browse every crop in the UK growing guides, or use the UK site directory.
Last updated 4 July 2026
Turn This Month's Jobs Into A Plan
Month-by-month advice works best when it becomes a written sowing list, bed plan, and follow-up task list.
Keep going
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.