Gardening jobs for September

September is the official start of autumn but the frosts don't usually arrive for a month yet and the leaves are still on the trees. Enjoy the last of the summer displays and keep them going for as long as possible by feeding and deadheading.

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Gardening maintenance for September

Prepare your lawn for winter

While the weather is still relatively warm and moist, it’s a good time to give your lawn some TLC after the rigours of summer.

• If moss is ruining the look of your lawn, apply a mosskiller or a combined feed, weed and mosskiller.
• After any moss is dead, set the blades on your mower a little lower than your normal cut height to make the other jobs easier.
• Rake the lawn to remove moss, thatch and other debris. Scarifying is a more aggressive approach that uses a mechanical device.

Mulch bare soil

As crops and flowers are lifted and the ground becomes free, mulch it with 3-5cm of well-rotted manure, spent mushroom compost or garden compost. Over the course of the year, worms will pull it into the soil, so there’s no need to dig or fork it in.

Learn how to make compost

Keep on top of weeds

Weeds can grow quickly at this time of year, so don’t be ashamed if you find some whoppers. The best way to keep on top of things is by hoeing and hand weeding once a week. Only put annual weeds on the compost heap, as perennial ones can regrow from their roots.

Try one of the best weed suppressing membranes

Lay turf

September is a great month for laying turf to create a new lawn or to repair an existing one. The soil is warm enough for the roots to grow before the colder weather arrives.

Learn how to lay turf, plus the best turf suppliers

Watch out for powdery mildew

Powdery mildew often affects both ornamental and edible plants in early autumn. You can use a fungicide on ornamental plants, but there are none available for edible plants. We recommend watering plants regularly as a way to prevent the disease.

Read more about how to treat powdery mildew on plants

Remove greenhouse shading

As light levels begin to decrease, it’s time to remove shading from the greenhouse. Shade netting can simply be removed and stored for next year, while shading paint needs to be rubbed off. Whichever type of shading you used, give the outside of the glass a thorough clean afterwards to let in the maximum amount of light.

Our guide explains how to choose the right greenhouse for you

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Grow-your-own-veg jobs for September

Harvest crops

Pumpkins and squash should be raised off the ground to ripen in the sun before harvesting. If the weather is wet, cut them early and bring them in to ripen in a greenhouse or sunny windowsill. To cure the fruits for storage, keep them in a warm room for a fortnight, then put them somewhere dry and cool but frost-free.

Early varieties of apples, such as 'Discovery', are best picked and eaten as soon as they're ripe. 

Sow winter salads

Early September is the best time to sow salad plants for harvests between November and early May. Grow them out of the worst of the weather under a protective covering, such as glass, polythene, fleece or insect-proof mesh. Although no extra heat is needed, without any protective covering harvests are small in winter and of lower quality.

Sow in modular trays using a Best Buy compost for sowing seeds and then plant outside when they're big enough to handle next month.

Winter salads to try:

• Chervil – sow asap for small harvests of fine flavour.
• Chicories and endives– small harvests of bitter and pretty leaves.
• Claytonia – very hardy, and prolific in mild winters.

• Corn salad – for harvests from November to April.
• Land cress – sow asap for small harvests of strong flavours, and beware pigeons.
• Lettuce – to stand as small plants then heart up in spring or for regular picking of outer leaves from November to May.
• Mizuna – for plentiful leaves in autumn and occasional winter harvests.
• Mustards – large leaves in mild weather.
• Salad rocket – crops in small amounts through the winter.
• Spinach ‘Medania’ – sow asap for small, steady and sweet harvests.

Make late sowings

There is just time in the first week of September to sow spring onions and cabbage, either direct or in modules for planting outside in early October: sow three cabbage seeds per module, and thin to one or two; and up to 10 spring onion seeds per module to plant as a clump that you can gradually thin next spring as you harvest the onions. These will grow through the winter and give crops next year.

Plants-and-flowers jobs for September

Buy spring bulbs

Most bulbs are ready to plant straight away, with the exception of tulips, which are best left until November to avoid the disease tulip fire. Whether you’re buying online, or in a garden centre or supermarket, look for named varieties and buy the biggest size bulbs you can for the best display of flowers. Plant the bulbs at three times the height of the bulb.

Find out more about how to grow tulips and the best varieties

Get ready for spring

Spring might seem like a long way off, but September is the perfect month to start making preparations for a beautiful floral display.

Plant spring bedding, such as pansies, wallflowers and sweet Williams. There should be a good selection of plants at the garden centre. Water them well before planting and give them a good soak whenever the weather is dry to help them establish quickly.

Try one of the best watering cans from the Which? Gardening magazine tests

Keep the patio going

Enjoy the summer display right to the end by keeping your containers in shape. 

Deadhead the plants regularly to encourage more blooms. If the weather is dry, give them a good soak and finally, give them an extra boost by feeding weekly with liquid fertiliser; controlled-release feeds will be running out of steam by now.

See our best liquid plant feeds

Divide perennials

Autumn is a good time to divide clumps of perennials such as hardy geraniums. Lift the clump and then divide it into pieces, either by prising it apart with two forks or cutting it up with a spade or bread knife.

Each piece needs some leaves and roots. Older pieces from the centre of the clump should be thrown away, but newer pieces can be replanted or shared with friends. 

Some perennials, such as sedums, will benefit from being divided every few years to keep the clump growing vigorously.

Feed oriental hellebores

It may seem a strange time of year to be thinking of a spring-flowering plant, but now is the time to feed hellebores. Calcified seaweed is great for the job, but a general feed, such as Growmore, would also work well. After feeding, mulch around the plant, ideally with spent mushroom compost.

Learn how to grow hellebores