Your September Gardening Checklist

Vegetable Tasks

Lift and store onions and potatoes – Get them out of the ground before autumn rains. Cure onions in the light, but store potatoes somewhere dark to prevent greening.

Cut courgettes and marrows regularly – They’ll stop producing by the end of the month.

Finish outdoor tomato crops – Pick remaining green fruits and ripen them indoors in a drawer, paper bag, or shoebox.

Plant out spring cabbage – Firm in well and protect with fleece or netting against pigeons and caterpillars.

Earth up leeks and stake Brussels sprouts – This keeps stems sturdy and blanched through windy autumn weather.

Cut back leaves shading pumpkins and squash – Let the sun ripen the skins properly for winter storage.

Pot up herbs like chives, mint, and parsley to bring them onto a sunny windowsill for winter use.

What to Grow

September is a great time to sow a variety of vegetables that thrive in cooler temperatures. These crops either mature quickly for autumn harvests or overwinter for an early spring start.

Spinach – Perfect for autumn sowing, thriving in cool soil. Fast-maturing varieties like ‘Bloomsdale’ will give quick yields.

Radishes – Rapid growth (25–35 days), making them an excellent late-season crop.

Collard Greens – Hardy and sweeter after a touch of frost; ideal for overwinter growing.

Kale – Sow now for continuous harvests through autumn and winter.

‘Cavolo Nero’ is a popular, cold-hardy choice.

Broad Beans – Sowing now allows strong root systems to establish before winter, giving earlier spring harvests.

Arugula (Rocket) – A fast-growing leafy green, perfect for quick cut-and-come-again pickings.

Pak Choi – Grows quickly in cool weather, providing crunchy leaves and stems in just a few weeks.

Mustard Greens & Land Cress – Great hardy salad options that can keep you harvesting even in the cold.

Spring Onions & Shallots – Sow hardy types now for an early start next year.

Pest & Disease Watch

Wasps – Particularly troublesome around ripening fruit. Pick fruit as soon as it’s ready and clear windfalls quickly. Hang wasp traps if needed, but remember they also eat aphids and caterpillars.

Cabbage white butterflies & caterpillars – Still active on brassicas. Check plants daily and remove eggs (yellow clusters on leaves) and caterpillars by hand. Netting helps keep them at bay.

Whitefly in greenhouses – Clouds of tiny white insects can weaken tomatoes, peppers, and cucumbers. Use sticky traps, good ventilation, and wash leaves with insecticidal soap if infestations build.

Slugs and snails – Autumn rains bring them back in force. Protect young seedlings with beer traps, copper barriers, or organic pellets. Check under pots and boards where they hide.

Leek moth and allium leaf miner – Both can attack leeks, onions, and garlic this month. Look for white mining trails or distorted leaves; cover with insect-proof mesh if you’ve had problems before.

Carrot fly – Late flights can still damage crops. Lift carrots promptly or use fleece/mesh to protect them.

Powdery mildew – Common on courgettes, marrows, and squashes as nights cool. Remove badly affected leaves and water plants at the base to reduce stress.

Blight on potatoes and tomatoes – Warm, wet spells can trigger outbreaks. Remove and dispose of infected foliage immediately (do not compost).