September is a transition month in the UK garden. Summer crops are still being harvested, but the focus quickly shifts toward autumn sowing and preparing for winter and early spring growth.
While daylight hours begin to shorten and temperatures gradually drop, September is still a highly productive sowing month—especially for fast-growing crops and hardy vegetables that will overwinter.
In this guide, we’ll cover exactly what to sow in September in the UK, including vegetables, herbs and flowers that thrive in cooler conditions and help extend your growing season.
Quick Answer: What Can You Sow in September?
September is ideal for fast crops and overwintering vegetables.
September is all about extending harvests and protecting soil for winter.
Vegetables to Sow in September
Winter Lettuce
September is one of the best months to sow hardy lettuce varieties.
Recommended types:
- Winter Density
- Arctic King
- Valdor
- All Year Round
Tip: Use cloches or cold frames for protection as temperatures drop.
Spinach (Hardy Varieties)
Spinach is ideal for autumn sowing and overwintering.
Benefits:
- Cold tolerant
- Early spring harvests
- Low maintenance
Rocket
Rocket continues to grow well in cooler conditions.
- Fast germination
- Continuous harvesting possible
Radishes
Radishes remain one of the fastest and most reliable crops in September.
Harvest often in 3–5 weeks.
Spring Onions
A strong succession crop for autumn and early winter.
Lamb’s Lettuce (Corn Salad)
One of the best overwintering salad crops.
- Extremely hardy
- Sweet flavour in cold weather
- Excellent for winter salads
Pak Choi and Asian Greens
September sowing produces excellent autumn harvests.
Best varieties:
- Pak choi
- Mizuna
- Tatsoi
- Mustard greens
Tip: Protect young plants from flea beetles.
Kale (Early Autumn Sowing)
In milder UK regions, early September sowings can still establish winter kale crops.
Broad Beans (Late Sowings)
In southern and sheltered areas, some gardeners sow broad beans in late September for overwintering.
- Strong spring growth
- Early harvest advantage
Herbs to Sow in September
Parsley
September is a great time to sow parsley for overwintering.
- Slow to germinate
- Reliable through cold months
Coriander
Best sown in small batches due to fast bolting in warm spells. In cooler September, it's less prone to bolt.
Chives
Hardy perennial herb suitable for sowing or dividing.
Flowers to Sow in September
Sweet Peas
September sowing produces strong root systems and earlier spring flowering. Protect from mice and slugs.
Cornflowers
Can still be sown early in September for late blooms or overwintering seedlings for an early show next year.
Calendula
Continues to flower into autumn and attracts pollinators, a cheerful late-season addition.
Nasturtiums
Still viable in early September for fast autumn growth and edible flowers/leaves before the first hard frost.
Green Manure Crops (Very Important in September)
September is one of the best months to protect and improve soil health in beds that have finished cropping.
Popular options:
- Winter rye
- Clover
- Mustard
- Phacelia
Benefits:
- Prevent nutrient loss from heavy rains
- Suppress weeds over winter
- Improve soil structure and add organic matter for spring
What Can Be Planted Outdoors in September?
Planting slows, but several crops can still go into the ground:
- Winter lettuce seedlings
- Spinach transplants
- Spring cabbage plants
- Garlic (late September in some regions)
- Onion sets (autumn planting varieties)
MyGrowPal helps you prepare for the colder months. Set your UK postcode and the app optimises sowing dates for overwintering crops and reminds you when to install protective covers like cloches or fleece.
September Gardening Jobs
Harvest Remaining Summer Crops
Continue to pick tomatoes, courgettes, beans, cucumbers, and herbs regularly. The more you pick, the more they produce until the first hard frost!
Prepare for Winter
Start planning for cold weather. Get your cold frames, cloches, and horticultural fleece ready. Consider insulating greenhouse walls for overwintering tender plants.
Soil Preparation
As summer crops finish, clear beds and add plenty of compost or well-rotted manure. This gives the organic matter time to break down and enrich the soil for next spring.
Weed Control
Autumn weeds still grow actively, especially after summer rains. Remove them early to prevent them from taking hold and going to seed, saving you work next year.
Succession Sowing
Maintain continuous harvests by regularly sowing small batches of fast-growing crops like lettuce, radishes, spinach, and spring onions.
Common September Sowing Mistakes
Thinking the Season Is Over
One of the biggest mistakes is assuming that with summer's end, the gardening season is over. September is actually a key winter-preparation month, offering vital sowing opportunities.
Not Using Protection
While days can be mild, cold nights can quickly damage young, tender seedlings. Failing to use cloches, cold frames, or fleece for newly sown or transplanted crops can lead to losses.
Overwatering in Cooler Weather
As temperatures drop and daylight shortens, soil retains moisture for longer. Overwatering can lead to damping off and root rot in young seedlings. Check soil moisture before watering.
Ignoring Winter Crops
Failing to sow overwintering crops like winter lettuce, spinach, broad beans, and garlic in September means missing out on valuable early spring harvests.
Using MyGrowPal to Plan September Sowing
September is a planning-heavy month where gardeners transition from summer productivity to winter preparation.
MyGrowPal helps simplify this shift by turning seed collections into a structured, seasonal growing system.
Frequently Asked Questions
Is September too late to sow vegetables in the UK?
No. September is ideal for overwintering crops and fast-growing salads.
What vegetables can I sow in September?
Winter lettuce, spinach, rocket, radishes, spring onions, kale and lamb’s lettuce all work well.
Can I grow lettuce in September?
Yes. Winter varieties are especially suitable.
What flowers can I sow in September?
Sweet peas, cornflowers and calendula are good options.
What should I focus on in September gardening?
Focus on winter preparation, soil improvement, and sowing overwintering crops.
Final Thoughts
September is a crucial transition month in the UK gardening calendar. While summer crops are still being harvested, forward-thinking gardeners use this time to establish overwintering vegetables and prepare for early spring growth.
By combining late harvests with smart autumn sowing, you can extend productivity well beyond summer.
And with MyGrowPal, you can manage this seasonal shift effortlessly—tracking seeds, planning winter crops, managing sowing schedules and staying organised as your garden moves into its next phase.