What to sow in September

Keeping the garden productive with winter veg

As summer fades into autumn, September in the UK still offers a surprising range of vegetable seeds that can be sown for late harvests or overwintering. With cooler nights and shorter days, it’s important to choose crops suited to the changing season. Many of these vegetables prefer mild conditions, and some will thrive with a little protection under cloches, cold frames, or greenhouses.

Don’t forget you can also plant in pots if space is at a premium, and a cloche can be as simple as a five litre water bottle with the bottom removed and holes poked in the sides for air flow.

Below we will discuss some potential crops to sow in September to keep the garden productive.

Spinach (Spinacia oleracea)

Spinach seeds are small, angular, and slightly rough to the touch. They can be sown directly in the soil or in seed trays for later transplanting. Sow seeds about 1/2 to 1 cm deep. In September sowing, direct sowing works well in moist, fertile soil. They prefer a sunny spot but will also tolerate light shade, especially in early autumn. spinach seeds are big enough to handle so plant seeds about 7–10 cm apart. If planting in rows keep a spacing of around 20 – 40 cms between rows. Keep the soil consistently moist but not waterlogged. Spinach seeds will germinate in about 7–14 days at temperatures between 10–20°C. Plants will be ready to harvest in 6–8 weeks, and if you take the outer leaves first you will be able to harvest for months to come.

• Seed shape: small, angular, rough
• Germination: 7–14 days, 10–20°C
• Position: sunny or partial shade
• Maturity: 6–8 weeks
• Watering: consistent, moist soil

Pests & Protection: Spinach is vulnerable to slugs, snails, and leaf miners. Protect young seedlings with cloches or net, use beer traps, finely crushed egg shells, or wool pellets against slugs. Vile as it sounds handpicking slugs at dusk can help keep down the slimy slug population. Companion planting with onions and garlic helps deter leaf miners. If leaf miner occurs, remove affected leaves when first detected.

Spring Onion (Allium fistulosum)

It’s not too late to try a sowing of these tiny, black, and angular seeds. Best sown directly into shallow drills outdoors, but you can also start them in seed trays to transplant later. Germination takes 10–21 days at 13–21°C. They thrive in sunny, well-drained soil and are ready in 8–12 weeks

• Seed shape: tiny, black, angular
• Sowing depth: 1 cm
• Row spacing: 15–20 cm apart, thin seedlings to 2–3 cm
• Germination: 10–21 days, 13–21°C
• Position: full sun, well-drained soil
• Maturity: 8–12 weeks
• Watering: light, regular moisture

Pests & Protection: Vulnerable to onion fly and thrips (thunder flies). Use fine mesh netting, encourage ladybirds, and interplant with carrots.

Cauliflower – All Year Round (Brassica oleracea var. botrytis)

Cauliflower seeds are small, round, and dark brown. The “All Year Round” variety can be sown in September through to late October. They can be sown in seed trays or modules, ready for transplanting outdoors once young plants are sturdy. Germination takes 7–12 days at 15–20°C. Cauliflower prefers firm, fertile soil in full sun and benefits from steady watering. Maturity is usually 20–26 weeks, making it a longer-term crop but one well worth the wait for dense, tasty curds (the white part of the cauliflower).

• Seed shape: small, round, dark brown
• Sowing depth: 1 cm
• Row spacing: 60 cm apart, thin or transplant seedlings to 50 cm spacing within rows
• Germination: 7–12 days, 15–20°C
• Position: full sun, fertile, firm soil
• Maturity: 20–26 weeks
• Watering: steady, consistent moisture (avoid drought stress)

Pests & Protection: Cauliflower is vulnerable to cabbage white butterflies, pigeons, clubroot, and aphids. Protect seedlings with fine mesh netting to prevent caterpillars and bird damage. Firm the soil well when transplanting. Interplant with celery, dill, or nasturtiums to deter pests. Regular checks for aphids can be managed with a neem oil spray or by encouraging beneficial insects such as ladybirds. When using neem oil, follow the instructions on the bottle and don’t overconcentrate the solution. Too concentrated will leave too much oil on your plants that will easily fry in the sun.

Lettuce (Lactuca sativa)

Lettuce seeds are tiny, oval, and flat. They germinate in 7–10 days at 10–18°C. Can be direct sown under cloches or started in trays. Prefers sun or light shade. Plants mature in 6–10 weeks and need consistent moisture. Lettuces also do really well in pots, just make sure the pot has the depth of at least 50 cm. so they can put down strong root.

• Seed shape: tiny, oval, light brown
• Sowing depth: 0.5 cm (surface sow with light covering)
• Row spacing: 25–30 cm apart, thin seedlings to 15–20 cm
• Germination: 7–10 days, 10–18°C
• Position: sunny or partial shade
• Maturity: 6–10 weeks
• Watering: regular, avoid waterlogging

Pests & Protection: Lettuce is susceptible to slugs, snails, and aphids. Use beer traps, seaweed mulch, netting and encourage beneficial insects. Interplant with chives or garlic for natural deterrence. Again it may sound gross, but hand remove slugs at dusk if possible. If growing in pots get yourself some copper electricians taps and wrap it round the middle of your pot. It is said that slugs and snails won’t slither over the tape. Although I have to say that’s no guarantee 😊

Radish (Raphanus sativus)

Radish seeds are small, round, and reddish-brown. They germinate in 4–7 days at 8–20°C. Quick-growing, they dislike transplanting, so sow direct. Maturity in just 3–4 weeks

• Seed shape: small, round, reddish-brown
• Sowing depth: 1 cm
• Row spacing: 15 cm apart, thin seedlings to 2–3 cm
• Germination: 4–7 days, 8–20°C
• Position: full sun, light soil
• Maturity: 3–4 weeks
• Watering: regular to prevent splitting

Pests & Protection: Vulnerable to flea beetles and cabbage root maggots. Use horticultural fleece and companion plant with nasturtiums as trap crops. Rotate to prevent soil-borne pests.

Pak Choi (Brassica rapa var. chinensis)

Pak choi seeds are small, round, and dark brown. They germinate in 7–10 days at 10–25°C. Can be direct sown or in seed trays to transplant later. Plants mature in 6–8 weeks, thriving in sun or partial shade.

• Seed shape: small, round, dark brown
• Sowing depth: 1 cm
• Row spacing: 30 cm apart, thin seedlings to 20–25 cm
• Germination: 7–10 days, 10–25°C
• Position: sunny or partial shade
• Maturity: 6–8 weeks
• Watering: consistent, avoid drying out

Pests & Protection: Targeted by cabbage whites, flea beetles, and slugs. Use fine mesh netting, organic straw mulches, and beer traps. Companion plant with mint or dill to confuse pests

Broad Beans (Vicia faba)

Broad beans are large, flat, and kidney-shaped. Sow direct in drills for overwintering. Seeds germinate in 7–14 days at 8–15°C. They prefer sun and fertile soil. September sowings mature in spring–early summer. Broad beans also do really well in pots, as ever just make sure your pots are deep enough.

• Seed shape: large, flat, kidney-shaped
• Sowing depth: 5 cm
• Row spacing: 45 cm apart, plants 20 cm within rows
• Germination: 7–14 days, 8–15°C
• Position: full sun, fertile soil
• Maturity: harvest in spring–early summer
• Watering: water well when pods form

Pests & Protection: Often attacked by blackfly. Prevent by pinching out growing tips after flowering. Encourage ladybirds and plant marigolds or nasturtiums nearby as diversions. Cloches protect overwintered seedlings from slugs.

👉 In summary, September in the UK and potentially other more temperate climates still provides plenty of opportunities to sow seeds. By paying attention to sowing depth, row spacing, and organic pest management, you can enjoy organic crops throughout the autumn and winter months.

If you enjoyed this post or found it useful please consider subscribing to the solitaire gardener community. Subscribing is free and will keep you up to date with posts and exclusive content directly to your inbox. Just type your email address in the box below and hit the subscribe button.

Thanks for reading Solitaire Gardener.