Month by month
Garden jobs for September: what to do in the garden
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| This month | This month in September |
September is one of the best months of the gardening year. The soil is still warm from summer, rain usually returns, and the light is soft and golden. Borders are full of late colour, while trees start to hint at autumn. In Scotland and northern England, the first light frosts can arrive towards the end of the month, especially in rural valleys, so keep an eye on the forecast if you grow tender plants. Further south, frost is more likely to hold off until late October or November. Use this window to plant, divide and plan, because roots established now give plants a head start next spring.
Flowers and borders
Start planting spring bulbs. Daffodils benefit from going in early, as they start to root in autumn; plant them at about three times their own depth. Crocuses, alliums and snowdrops bought as dry bulbs can go in now too, although snowdrops establish more reliably when planted “in the green” in late winter.
Clumps of perennials that have become congested or bare in the middle can be lifted and divided once they’ve finished flowering. Hardy geraniums, catmint, heuchera and achillea all respond well. Lift the clump with a fork, split it with two forks back to back or a sharp spade, discard the tired centre and replant the vigorous outer pieces in soil refreshed with compost. Water them in well.
It’s also a great month to plant new perennials, shrubs and evergreen hedges, as the warm soil helps roots grow before winter. Biennials such as foxgloves and wallflowers can be planted out in their flowering positions. Leave seed heads that look good, such as those of sedum and ornamental grasses, as they provide structure and shelter for insects through winter.
Vegetables
Lift maincrop potatoes on a dry day, leave them on the surface for a few hours to dry, then store them in hessian or paper sacks somewhere dark and frost-free. Harvest pumpkins and winter squash when the skin is hard and the stalk has started to crack; leave them in the sun for a week or two to cure, which helps them keep for months.
Sow hardy salad leaves, winter purslane and lamb’s lettuce in a sheltered spot, and plant overwintering onion sets and the first garlic cloves towards the end of the month. In colder northern gardens, garlic does well planted now so it gets established before the ground gets cold.
Fruit
Apples and pears are ripe when they come away easily with a gentle lift and twist. Early varieties don’t keep well, so eat them fresh; later varieties can be stored in a cool shed, wrapped individually in paper and checked regularly for rot. Pears are best picked while still firm and ripened indoors. Cut out fruited canes of summer raspberries if you haven’t already, and order bare-root fruit trees and bushes for winter planting.
Lawns
September is the best month to sow a new lawn or overseed thin patches. Rake out thatch and moss with a spring-tine rake, spike compacted areas with a garden fork, and topdress with a mix of sieved soil and sharp sand. Apply an autumn lawn feed, which is lower in nitrogen than spring feeds, if the grass is looking hungry. Our lawn care calendar walks through scarifying, aerating and overseeding.
Wildlife
Leave some areas of the garden untidy, with hollow stems and piles of leaves, as homes for overwintering insects. Clean out bird boxes once you’re sure they’re empty, using boiling water rather than chemicals. Ivy flowering on walls and fences is one of the last big nectar sources of the year for bees, wasps and late butterflies.
Indoors and under cover
Bring tender plants such as pelargoniums and fuchsias that aren’t fully hardy into a greenhouse or cool porch before the first frost. Clean the greenhouse glass to let in as much light as possible over winter. Keep picking the last tomatoes and peppers, and ripen green tomatoes indoors on a windowsill next to a banana.
Plants looking good this month
Early autumn colour comes from Japanese anemones, Michaelmas daisies, sedum, rudbeckia and the arching plumes of miscanthus. Watch out too for the first berries on rowan trees, which birds strip quickly.
Looking back or ahead? See August jobs or move on to October jobs.
From the plant finder
In flower in September
Good time to plant
Due for pruning
Grow your own in September
Sow now
Plant out
Ready to harvest
Problems to watch for in September
Spotted something else? Diagnose it by symptom.