What to plant in September in the UK

Use this september checklist as a seasonal starting point, then check local frost, weather and the needs of each species.

September checklist

• Move tender plants before cold nights.
• Reduce feeding as growth slows.
• Keep new arrivals sheltered while they settle.

Plants we grow: what to do in September

• Coleus: Pot up indoors, Take cuttings, Bring indoors. A houseplant all year that can summer outside once frosts are over. Bring it back in before nights drop below about 10°C.
• Tradescantia, Callisia and inchplants: Pot up indoors, Take cuttings. Indoor trailing plants that can be potted up any month. Pinch and root the tips in spring and summer for bushier pots.
• Kalanchoe and Mother of Thousands: Pot up indoors, Take cuttings. Succulent houseplants for a bright windowsill all year. Keep them on the dry side in winter. Toxic to pets.
• Cacti and trailing succulents: Pot up indoors. Pot up any month in gritty compost. Water sparingly from November to February while growth rests.
• Terrarium and foliage houseplants: Pot up indoors. Indoor and terrarium plants that can be planted any month. Keep them out of cold draughts and hot radiators in winter.
• English ivy: Pot up indoors, Plant outside, Take cuttings. Hardy, so it can live indoors or go outside in spring or early autumn.
• Tomatoes: Harvest. Tender. Plant in a greenhouse from April or outside once the last frost has passed.
• Cucumbers and cucamelons: Harvest. Tender and frost-sensitive. Grow on under cover until June, or keep in a greenhouse.
• Melons and watermelons: Harvest. Needs warmth. A greenhouse or sunny sheltered spot gives the best crops.
• Courgettes: Harvest. Plant outside after the last frost. Pick often to keep the crop coming.
• Squash and pumpkins: Harvest. Tender. Plant into rich soil once frosts are over and cure the fruit in the sun before storing.
• Runner beans: Harvest. Tender. Plant at the foot of canes after the last frost.
• French, climbing and yard-long beans: Harvest. Tender. Plant out after the last frost. Yard-long beans do best in a greenhouse.
• Kohlrabi: Harvest. Hardy. Harvest when the swollen stems are tennis-ball sized.
• Leafy greens and brassicas: Plant outside, Harvest. Hardy, cut-and-come-again leaves. Late summer plantings crop into autumn.
• Sunflowers: In flower. Plant out after the last frost in full sun. Stake the tall varieties.
• French marigolds: In flower. Tender bedding. Plant after the last frost. A good companion for tomatoes.
• Calendula (pot marigold): Plant outside, In flower. Hardy annual. Deadhead to keep the flowers coming.
• Cosmos: In flower. Tender annual. Plant after the last frost in a sunny spot.
• Cornflowers: In flower. Hardy and loved by pollinators. Plant out in spring.
• Borage: In flower. Hardy annual with edible blue flowers. Often self-seeds.
• Nasturtiums: In flower. Tender. Plant after the last frost. Flowers best in poor soil.
• Balloon vine: In flower. Tender climber. Plant against a warm, sunny support in June.

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