Expert Garden Tips & Advice for September 2026 Aug 31

September is one of the most rewarding and exciting months in the gardening calendar especially after the extended extreme heat we have experienced this Summer. The first gentle shift in the air signals the turn of the season — mornings carry a welcome freshness, evening light softens to gold, and the garden begins its magnificent autumn transformation. Far from winding down, September is a month of real purpose and productivity: there is much to harvest, much to plant, and much to do in preparation for the seasons ahead.

It is also the month when we begin to look forward — to spring bulbs going into the ground, to the bare-root rose and tree season approaching, and to the quiet satisfaction of a garden prepared and put to bed well. Below are our exclusive Heritage Gardens gardening tips and advice for September 2026, provided by our own garden expert.

🍂 The September Garden — What to Expect

September brings a marked change from the heat of August. Daytime temperatures across the UK typically range from 14°C to 20°C, though warm sunny spells — the much-loved Indian summer — can extend well into the month. Nights are noticeably cooler and, in northern parts of the UK and exposed locations, the first ground frosts may arrive by the end of September. Keep an eye on the forecast and be ready to bring tender plants under cover or protect them with fleece if frost threatens.

Soil temperatures remain warm enough through September to support planting and sowing, making it an excellent month for establishing new plants before winter. Any plants put in now will have time to settle their roots before the cold truly arrives.

🌿 Lawns

• Autumn lawn renovation — September is the single most important month for lawn care. All lawns have suffered during the Summer & turned a  shade of yellow from  drought, — now is the time to address it. Scarify, aerate and overseed in one coordinated programme for the best results.
• Scarifying — Use a spring-tine rake or mechanical scarifier to remove the build-up of thatch (dead grass and moss) from the lawn surface. This allows air, water and nutrients to reach the roots effectively. Rake out the debris thoroughly afterwards.
• Aerating — Spike the lawn with a garden fork or hollow-tine aerator to relieve compaction, particularly in heavily used areas. Push the fork in to around 10–15cm (4–6in) and work across the whole lawn in a grid pattern.
• Overseeding — After scarifying and aerating, overseed any bare or thin patches with a suitable grass seed mixture. Rake lightly to cover the seed with a thin layer of soil and water in well. Keep the seed moist until germination — usually 7–14 days in warm conditions.
• Autumn lawn feed — Apply a specialist autumn lawn fertiliser — one that is low in nitrogen and higher in phosphate and potash. This strengthens grass roots for winter without promoting the soft leafy growth that would be vulnerable to frost and disease.
• Mowing —  Light mowing as the green colour starts to reappear with the recent rain but begin to raise the cutting height slightly as growth slows. By the end of September, reduce mowing frequency and aim for a height of around 4cm (1.5in) going into autumn.
• Fallen leaves — Remove fallen leaves from the lawn regularly. A heavy covering of wet leaves blocks light and air and will quickly cause the grass beneath to yellow and die off. Collect leaves for composting or leaf mould.

🌸 Borders, Flowers & Bulbs

• Plant spring bulbs now — September is the beginning of the spring bulb planting season. Daffodils, alliums, muscari (grape hyacinth), crocus and scilla can all go in this month. The golden rule is to plant bulbs at a depth of approximately three times their own diameter. Tulips are best left until October or November to reduce the risk of tulip fire disease.
• Divide perennials — September is an excellent time to lift and divide overgrown clumps of herbaceous perennials such as hostas, hemerocallis (daylilies), geraniums, astilbes and rudbeckias. Dividing them now allows the new sections to establish roots before winter. Discard the woody centre of old clumps and replant the healthy outer sections.
• Cut back spent perennials — Begin cutting back the faded stems of summer perennials. However, consider leaving the seed heads of plants such as Rudbeckia, echinacea, sedums and teasels standing through autumn and winter — they provide valuable food for birds and add beautiful structural interest to the winter garden.
• Collect seeds — Gather seed from plants you wish to propagate next year. Choose a dry day, collect seeds into labelled paper envelopes and store in a cool, dry, dark place. Many hardy annuals and perennials come reliably true from seed.
• Dahlias and tender plants — Dahlias will continue to flower until the first frost. Keep deadheading regularly. Once the foliage has been blackened by frost, cut stems back to around 15cm (6in), lift the tubers carefully and store them in a frost-free location in dry compost or sand over winter.
• Late summer colour — Sedums, Asters, Rudbeckias, Japanese Anemones and Nerines are all at their most beautiful in September and will carry the border through to the frosts. Enjoy them — and the bees and butterflies they attract.

🌳 Trees, Shrubs & Climbers

• Plant new trees and shrubs — September marks the beginning of the best planting season for trees and shrubs. The soil is still warm, encouraging root establishment, while the cooler air reduces water stress on new plants. Container-grown plants can be planted now; the bare-root season for roses, hedging and fruit trees begins later in October/November.
• Roses — begin planning — September is the perfect time to plan new rose plantings for the bare-root season ahead. Visit gardens and nurseries this month to see roses at their autumn best and make your selections. Prepare the ground now by digging deeply, incorporating well-rotted organic matter, ready for planting when bare-root roses arrive from November onwards.
• Autumn colour — September brings the first blush of autumn colour to the garden. Acers, Amelanchier, Sorbus, Euonymus, Virginia creeper and ornamental vines will all be developing their spectacular autumn livery this month — enjoy one of the garden year's most beautiful spectacles.
• Evergreen hedges — September is a good time to plant new evergreen hedging such as yew, box, laurel or Portuguese laurel. They will establish roots over the winter and put on strong growth next spring.
• Clematis — Group 3 pruning — Late-flowering clematis (Group 3) such as Clematis viticella varieties can be cut back hard now to around 30cm (12in) from the ground, or left until early spring if preferred. Mulch the base generously.
• Climbers — tidy and tie in — Check all climbers on walls, fences and arches. Tie in any long stems that could be damaged by autumn winds and remove any dead or diseased growth.

🥦 The Kitchen Garden — Vegetables, Fruit & Herbs

• Final tomato harvest — Bring in all remaining tomatoes before the first frost. Any green tomatoes can be ripened indoors on a warm windowsill or wrapped individually in newspaper and stored in a drawer — they will ripen slowly over several weeks. Alternatively, use green tomatoes for chutney.
• Plant garlic — September and October are ideal months to plant garlic. Choose a sunny, well-drained spot and plant individual cloves around 15cm (6in) apart and 5cm (2in) deep with the pointed end upwards. Garlic planted now will be ready to harvest next June or July.
• Continue harvesting — Apples, pears, plums, courgettes, squash, pumpkins, sweetcorn, French beans and late salads will all still be cropping well in September. Pick regularly and store carefully. Squash and pumpkins should be left on the plant as long as possible to develop a hard skin for winter storage.
• Sow winter salads and spinach — There is still time to sow winter lettuces, rocket, land cress, corn salad and spinach under cover or in a cold frame for salad leaves through autumn and winter. Outside sowings of these crops in sheltered spots are also worth trying.
• Clear and compost — As crops finish, clear the beds promptly. Remove all plant debris to reduce the risk of disease and pests overwintering. Add everything that is disease-free to the compost heap; burn or bin any diseased material.
• Sow green manures — Sow a green manure such as grazing rye or field beans on any cleared vegetable beds. This will protect the soil surface through winter, prevent nutrient leaching and add organic matter when dug in next spring.
• Pests to watch for — Slugs and snails become more active again as the weather cools and rainfall increases. Check under pots, debris and around tender plants regularly. Apple and pear scab can be prevalent — remove and destroy all fallen and scabby fruit rather than composting it.

🪴 Pots, Containers & Autumn Displays

• Clear summer containers — As summer bedding plants pass their best, clear them out and compost the contents. Clean the pots thoroughly before replanting with autumn and winter displays.
• Plant autumn containers — Create beautiful autumn displays using dwarf ornamental cabbages, winter pansies, cyclamen, heucheras, sedums, skimmia and trailing ivy. Add some early spring bulbs in the bottom of the pot beneath the compost to give a second season of interest from February onwards.
• Pot up spring bulbs — Plant daffodil, tulip and allium bulbs into pots now for a spectacular spring display on the patio. Use a good quality potting compost with added grit for drainage. Tulips in pots can be planted a little later, in October or November.
• Reduce watering — As temperatures fall and growth slows, reduce watering of containers significantly. Overwatering in cool autumn conditions is a common cause of root rot.

🦋 Wildlife, Ponds & the Autumn Garden

• Leave seed heads for birds — Resist the urge to tidy everything away. The seed heads of rudbeckia, echinacea, sunflowers, teasels and grasses provide a vital food source for finches and other seed-eating birds through autumn and winter. They also add beautiful structural interest to the winter border.
• Hedgehogs preparing for hibernation — Hedgehogs will be feeding voraciously this month to build up fat reserves before hibernation. Leave out a dish of dog or cat food and fresh water to help them. Create a log pile or leaf heap in a sheltered corner as a potential hibernation site.
• Bird feeders — Clean and refill bird feeders and baths as the natural food supply declines. Put out a mix of sunflower seeds, nyjer seeds and fat balls. Once you start feeding birds in autumn, try to continue regularly through to spring.
• Ponds — net falling leaves — As leaves begin to fall, net the surface of the pond to prevent them decomposing in the water, which depletes oxygen and releases harmful gases. Remove any aquatic plants that have died back and thin out vigorous oxygenating plants.
• Compost heap — September is the perfect month to turn the compost heap, adding the abundance of material produced by garden clearance. Ensure a good mix of green (nitrogen-rich) and brown (carbon-rich) material for the best results.

🍒 Plan Ahead for Roses — The Heritage Rose Collection

September is the ideal month to plan your rose planting for the season ahead. The bare-root rose season begins in November, and the finest varieties sell out early. At Heritage Gardens, our Heritage Rose Collection features a beautiful range of traditional and classic varieties — the roses that have graced English gardens for generations and that continue to be cherished for their extraordinary fragrance, their elegant blooms and their unique character.