What to do during September in your garden and greenhouse.
Your monthly gardening checklists
Flowers
- Sow hardy annuals, such as cerinthes, ammi, scabiosa and cornflowers, for flowers early next summer
- Lift gladioli corms, dry them off, then store in a frost-free shed or garage over winter
- Plant wallflowers, pansies, forget-me-nots and other spring bedding in pots and borders
- Collect ripe seeds from your favourite flowers and store in labelled envelopes, ready to sow in spring
- Plant up containers for autumn interest, using cyclamen, heathers, heucheras and other colourful bedding plants
- Lift, divide and replant congested clumps of perennials, such as achilleas, once they finish flowering
- Apply vine weevil control to pots if plants show the tell-tale sign of notched leaf margins
- Fill any gaps with late-flowering perennials, such as sedums, to provide nectar for pollinating insects into autumn
- Plant spring bulbs in autumn, including crocuses, daffodils, hyacinths, bluebells and snake's-head fritillaries in pots and borders
- Take cuttings from fuchsias, salvias and pelargoniums
- Keep summer bedding flowering in hanging baskets and pots until the first frosts by deadheading and feeding regularly
- Trim conifer hedges to neaten them up and control height
- Leave sunflower seedheads in place for birds to feed on
Greenhouse
- Plant prepared hyacinth bulbs in pots or hyacinth glasses, for fragrant indoor flowers at Christmas
- Take down greenhouse shade netting or wash off shading paint by the end of the month, as light levels start to fall
- Stay vigilant for pests and diseases in the greenhouse, and treat any you find immediately
- Plant dwarf spring bulbs in pots, including irises, crocuses, chionodoxa and scilla, for early flowers
- Pot up tender perennials, such as fuchsias and osteospermum, from summer displays and bring indoors before temperatures drop
- Plant Anemone De Caen corms for a vibrant indoor display in early spring
- Pay close attention to greenhouse ventilation, shutting vents on cool nights
- Check greenhouse heaters are in good working order, and find out how to keep the heat in this winter
- Maintain good plant hygiene, picking off faded blooms and dead leaves before fungal diseases can take hold
- Look out for forecasts of early frosts and be ready to bring tender potted plants under cover
- Move potted peaches and nectarines into a cool greenhouse or porch
Fruit and veg
- Sow hardy greens, such as kale, land cress, pak choi, mizuna, lamb's lettuce and mustard, for winter pickings
- Prune out all the fruited canes of summer raspberries, cutting down to the base, and tie in new canes to supports
- Pot up herbs, such as chives and parsley, and place on a sunny windowsill to use during winter
- Start sowing hardy varieties of broad beans and peas for early crops next year
- Plant shallot and onion sets in a sunny spot, 10cm apart, with the tip just showing above the soil
- Cut away any leaves covering the fruits of pumpkins, squash and marrows to help the skins ripen in the sun
- Plant saffron crocus bulbs (Crocus sativus), so you can harvest your own saffron this autumn
- Pick apples and pears before the wind blows them down, and store undamaged fruits if you can't eat them fresh
- Store chillies by threading the stalks onto strong cotton or wire and hanging up to dry somewhere warm and dry
- Cut off trusses of unripe outdoor tomatoes before the weather turns cold, then ripen them indoors
- Lift maincrop potatoes, dry off and store in hessian or paper sacks, in a cool, dark, well-ventilated place
- Complete summer pruning of both free-standing and trained apple trees, to encourage good fruiting in future years
House plants
- Feed house plants once a week with liquid fertiliser, continuing through to autumn
- Repot moth orchids after flowering if they look like they're about to burst out of their pot
- Water house plants less frequently and move them off particularly cold windowsills at night. Find out how to water your house plants
- Plant hippeastrum (amaryllis) bulbs in pots for spectacular flowers over the festive season
- Bring any house plants that you moved outside over summer back indoors, before temperatures start to drop
- Repot any house plants that have become top heavy or pot bound into larger containers
- Maximise the amount of light your house plants receive by moving to brighter spots, or choose indoor plants for low light
- Some house plants, like snake plants, are particularly prone to collecting dust on their leaves. So be sure to give these a wipe regularly
- Take leaf cuttings from house plants, including African violets and begonias
- Take leaf cuttings from succulents, such as echeverias, crassula and sedums
- Check your house plants for pests like aphids, scale insects, thrips and mealybugs
- Take large-leaved house plants into the garden and hose them down to clean off accumulated dust
For more house plant advice and inspiration visit our Growing and caring for house plants page. Find out how to rescue house plants in this podcast episode.
Garden maintenance
- Rake thatch from lawns, scarify well-trodden areas by spiking with a garden fork, and re-seed bare patches
- Put netting across ponds to stop autumn leaves falling in and rotting, and keep on top of autumn pond maintenance
- Water autumn-flowering asters regularly to deter mildew
- Clean out water butts and check downpipe fittings in preparation for autumn rains
- Remove duckweed, pondweed and algae from water features and ponds
- Check that tree ties and plant supports are firmly in place, ahead of any autumn gales
- Wash and disinfect bird feeders and tables to maintain hygiene
- Collect fallen leaves to store in a leaf mould bin made of chicken-wire or bin bags to make leaf mould
- Hunt for rosemary beetles on lavender and rosemary, picking off the striped metallic beetles and their grey larvae
- Collect up and bin apples, plums and pears infected with brown rot, to reduce the spread of this fungal disease
- Order bare-root fruit trees to plant later in autumn or winter
- Check roses for signs of fungal diseases, such as blackspot, and pick off and bin all affected leaves
Offers
Gardening offers
Double Trailing Fuchsia Collection - 25 for £25
With shades of pink, orange, magenta, and blue, these trailing blooms add elegance to any space. The collection features five gorgeous varieties, including RHS award-winners, flowering from summer to frost in pots or baskets.
£25
Supplied as 25 x young plants (5 of each).
Gardening offers
Datura Collection
Fondly known as the Angel's Trumpet, Datura have become increasingly popular recently as a patio and conservatory feature plant. Exotic looking plants with trumpets up to 25cm long. Our collection includes one each of Yellow, White, and Pastel Pink. Height 1.5m. Flowers July-September. Supplied in a 9cm pot.
£12.72
Supplied as 3 x 9cm pots (1 of each)
use code: DATURA15
Travel and events
Experience Madeira’s Enchanting Flower Festival with Adam Frost
Take a fascinating horticultural tour of beautiful Madeira and see the fabulous Flower Festival with Gardeners' World presenter Adam Frost.
From£2579
per person, based on two people sharing a room, subject to availability. 29 April - 6 May 2026.