Top Five Garden Jobs for September

Our recommendations on what to do this September.

As September arrives, whether you mark autumn from the 1st (meteorological autumn) or the equinox on the 22nd (astronomical autumn), there's no denying the cooler mornings and shorter days. This month is a mix of maintaining late-summer blooms and preparing for next year's garden. Here are the top jobs to focus on this September:

Watering

September tends to be warmer and drier now, with many regions experiencing a kind of extended summer. In the Solent, for example, rainfall averages only 53mm compared to October's 86mm. To keep summer flowers blooming until frost, regular watering is essential, especially for pots and baskets. Newly planted items also need consistent watering until established.

Indoor plants, however, require less water as daylight hours shorten. Start reducing how often you water them now, and bring any houseplants left outdoors back inside.

Collecting Seeds

Early autumn is the perfect time to collect seeds from your favourite plants, including annuals, biennials, and perennials. Seeds are ready to gather when they turn brown or black. Collect them on a dry day and let them dry out on a tray before storing them in paper bags or envelopes.

Don't forget to leave some seeds for wildlife, like sunflower seed heads for birds. To learn more, the RHS offers excellent advice on collecting seeds here. Seed Gathering Season also starts on 22nd September, and you can read about it on the UK Tree Council’s website [here].

Planting and Sowing

September is ideal for planting spring bulbs like crocuses, daffodils, and bluebells (save tulips for November). As a rule of thumb, plant bulbs at a depth three times their height.

It’s also time to sow hardy annuals, spring bedding plants, and vegetables. Varieties like peas, broad beans, kale, and mizuna can be sown now for early spring crops or winter salads. Fill gaps with late-flowering perennials such as Sedum and Rudbeckia to extend your garden's colour and provide nectar for pollinators.

Pruning and Trimming

After fruiting, prune berry bushes like blackberries, tayberries, and summer raspberries. Cut down the canes that have fruited and trim the new growth, leaving four to six strong canes per plant.

If your conifer hedges are looking unruly, now’s a good time to neaten them up as they’ll stop growing soon.

Harvesting and Storing

Many crops are ready to harvest in September. Dry chillies, store potatoes in paper or hessian sacks, and make chutney with green tomatoes. If your pumpkins and tomatoes are still ripening, remove some leaves to let the sun in.

September is also the time to show your lawn some love - rake, aerate, and reseed any bare patches. If the ground is too hard, wait a few weeks.

Whichever side you fall on regarding whether September is summer or autumn, there’s plenty to do in the garden. Keep flowers going for as long as you can and prepare for the cooler months ahead! And don’t forget if you need some help in the garden our garden maintenance teams are here to help.