What to Do in the Garden in September | UK Gardening Jobs
Discover what to do in your garden in September, including autumn planting, lawn care, fruit and vegetables, dividing perennials, weather advice and plants to enjoy.
What to do in my garden in September
September is one of the most important transitional months in the UK gardening calendar. Summer may still be very much in evidence at the beginning of the month, but shorter days, cooler nights and the first signs of autumn gradually begin to change the garden.
Late-flowering perennials, ornamental grasses and autumn berries can make September exceptionally colourful. At the same time, falling leaves, ripening fruit and slowing growth signal that it is time to begin preparing for the months ahead.
September is also one of the best months for planting. The soil usually remains warm from summer while increasing rainfall reduces the risk of new plants drying out. This combination creates excellent conditions for root establishment.
The priorities this month include planting, dividing suitable perennials, lawn renovation, harvesting fruit and vegetables, collecting seed and continuing to water recently planted trees and shrubs where conditions remain dry.
Top 10 tips
1. Start autumn planting
September can be an excellent month for planting container-grown trees, shrubs and perennials.
Warm soil encourages root development before winter.
2. Renovate tired lawns
September is traditionally one of the best months for lawn renovation.
Scarifying, aerating, overseeding and repairing damaged areas can all be considered where conditions are suitable.
3. Divide suitable herbaceous perennials
Many established perennials can be divided once flowering has finished.
Replant healthy sections and water them thoroughly.
4. Keep deadheading
Do not give up on summer-flowering plants too early.
Dahlias, roses, Salvias and many other plants can continue flowering well into autumn if regularly deadheaded.
5. Harvest fruit and vegetables
Apples, pears, tomatoes, beans, courgettes and numerous other crops may be ready for harvesting.
Pick regularly and store suitable crops correctly.
6. Collect seed
Collect ripe seed from favourite garden plants on dry days.
Label everything carefully before storing.
7. Plant spring-flowering bulbs
September is an excellent time to begin planting many spring bulbs.
Daffodils, Crocus, Alliums and other bulbs can be planted during autumn.
8. Continue watering new trees and shrubs
September can still be surprisingly dry.
Recently planted trees and hedges should not be forgotten simply because temperatures have fallen.
9. Check garden structures
Inspect fences, gates, pergolas, sheds and other structures before autumn storms become more frequent.
10. Start preparing for autumn
Clean gutters, clear drainage channels, check outdoor lighting and begin planning how tender plants will be protected later in the season.
Herbaceous Perennials
September can be one of the finest months for herbaceous borders.
Late-flowering plants combine with ornamental grasses to create a softer, more mature appearance than the bright growth of early summer.
Continue deadheading plants that are still capable of flowering.
These may include:
Dahlias
Roses
Salvias
Penstemons
Heleniums
Rudbeckias
Echinaceas
Japanese anemones
Persicarias
Do not automatically cut everything down as soon as flowering finishes.
Many seed heads provide excellent autumn and winter structure and can also support wildlife.
Echinacea, Rudbeckia, Phlomis, Sedum/Hylotelephium and ornamental grasses can remain attractive long after flowering.
September is also a useful month for dividing suitable established perennials.
Plants that have become congested, developed bare centres or flowered poorly may benefit.
Water newly divided plants thoroughly.
Continue removing perennial weeds while they are easy to identify.
Towards the end of the month, begin clearing plants that have genuinely collapsed or become diseased while retaining useful structural growth.
September begins another important planting period for trees and shrubs.
Container-grown plants can be installed throughout the month where conditions are suitable.
As autumn progresses, the availability of root-balled and bare-root plants will also begin to increase as plants enter dormancy.
September planting has several advantages.
The soil remains relatively warm, encouraging roots to establish, while cooler air temperatures reduce water loss from foliage.
Continue watering trees and shrubs planted earlier in the year during dry weather.
Check:
Tree ties
Stakes
Underground anchoring
Rootball stability
Mulch
Soil moisture
Adjust ties before autumn winds arrive.
Remove damaged or dead branches where appropriate, but avoid unnecessary pruning simply because autumn is approaching.
Many trees and shrubs should be pruned at specific times according to their flowering habit and susceptibility to disease.
September is also an excellent time to assess the structural planting within the garden.
Once herbaceous plants begin fading, gaps in evergreen structure can become much more obvious.
September is one of the key lawn-care months.
Cooler temperatures, increased rainfall and warm soil create excellent conditions for grass recovery and seed germination.
Where required, lawn renovation may include:
Scarification
Aeration
Overseeding
Top dressing
Repairing bare patches
Autumn feeding
Improving lawn edges
Scarification removes excessive thatch and dead material.
Aeration can improve air movement, drainage and root development, particularly on compacted ground.
Overseeding can help thicken sparse lawns.
Keep newly sown areas consistently moist until germination and establishment.
Continue mowing while grass remains in active growth, but gradually increase the mowing height as autumn progresses.
Remove fallen leaves regularly.
Leaves left sitting on lawns can block light and encourage deterioration beneath them.
September is also an excellent month to investigate areas that remained waterlogged during the previous winter and consider whether drainage or soil improvement is required.
September is a major month for tree fruit.
Many apple and pear varieties are ready for harvesting.
Different cultivars ripen at different times, so do not rely solely on colour.
A ripe apple or pear will often detach relatively easily when gently lifted and twisted.
Handle fruit carefully if it is intended for storage.
Bruised or damaged fruit should generally be used first rather than stored.
Late plums and damsons may also be ready.
Autumn-fruiting raspberries should be picked regularly.
Blackberries can continue producing heavily.
Remove fallen and damaged fruit from beneath trees to reduce potential pest and disease problems.
Continue checking stored fruit regularly.
Fruit trees planted during the year may still require watering during dry weather.
September is also a good time to assess cropping performance and identify fruit trees that may require pruning or additional pollination partners in future.
September can provide an enormous harvest from the vegetable garden.
Continue picking:
Tomatoes
Courgettes
Runner beans
French beans
Beetroot
Carrots
Potatoes
Sweetcorn
Cucumbers
Onions
Shallots
Harvest beans regularly while they remain tender.
Courgettes can quickly become oversized if left too long.
Outdoor tomatoes may need particular attention as temperatures fall.
Remove leaves that excessively shade ripening fruit where appropriate and continue monitoring for blight.
Maincrop potatoes can be lifted as foliage dies back and skins mature.
Allow potatoes intended for storage to dry before placing them somewhere cool, dark and frost-free.
Onions and shallots should also be dried thoroughly before storage.
September sowings can include suitable autumn and winter crops such as:
Spinach
Winter salads
Rocket
Radishes
Spring onions
Some oriental greens
Green manures can also be sown on vacant vegetable beds to protect and improve soil.
Many herbs remain productive during September.
Continue harvesting:
Parsley
Mint
Oregano
Thyme
Sage
Rosemary
Chives
Basil
Tender herbs such as basil will begin slowing as nights become cooler.
Harvest and preserve surplus leaves before temperatures fall significantly.
Herbs can be dried or frozen depending upon the species.
Perennial herbs may be divided where appropriate.
Remove damaged or diseased foliage.
Avoid cutting Mediterranean herbs hard into old woody growth.
Container-grown herbs should continue to be watered when necessary, although their requirements will gradually reduce as temperatures fall.
Consider moving tender herbs into protected conditions before the first frost.
September is a useful month for preparing ponds and water features for autumn.
Falling leaves can quickly become a problem.
Remove leaves from the water before they sink and decompose.
A temporary pond net may be useful beneath heavily shedding trees, provided it is installed safely and does not endanger wildlife.
Check:
Pumps
Filters
Reservoirs
Pipework
Fountains
Rills
Grilles
Lighting
Remove excessive dead aquatic foliage.
Thin vigorous pond plants where necessary.
Place removed aquatic vegetation beside the pond temporarily before disposal where appropriate, allowing small creatures an opportunity to return to the water.
Water evaporation generally begins slowing as temperatures fall.
Clean pumps and filters while conditions remain relatively pleasant.
This is also a useful time to inspect water features for leaks or maintenance issues before winter.
September is an excellent month to inspect hard landscaping before autumn and winter weather.
Check:
Porcelain paving
Natural stone
Paths
Steps
Driveways
Paving joints
Garden walls
Retaining walls
Drainage channels
Manhole covers
Raised beds
Remove weeds from paving joints.
Clear leaves and organic debris before they begin creating slippery surfaces.
Drainage becomes increasingly important as rainfall increases.
Clean channel drains, gullies and outlets.
Investigate persistent standing water rather than simply accepting it as an inevitable part of winter.
Check steps and paths for loose paving or trip hazards.
Cut back plants that have encroached onto access routes during summer.
September is also a good month to undertake landscaping work because soil and weather conditions can be more manageable than during the wettest part of winter.
Prepare garden structures for autumn winds and wetter weather.
Inspect:
Fences
Gates
Pergolas
Trellis
Privacy screens
Gazebos
Garden buildings
Arches
Raised beds
Tighten loose fixings and repair minor problems before storms expose them.
Climbing plants may still require tying in or pruning according to species.
Remove dead or damaged stems that could become detached in strong winds.
Clean gutters and downpipes on sheds, garden rooms and other buildings.
Check roofs for damage.
Outdoor furniture that will remain outside through winter should be cleaned and inspected.
Items that require dry storage can gradually be prepared for moving indoors.
Check garden lighting as evenings become noticeably darker.
September is an excellent time to adjust lighting positions that have become obscured by summer growth.
The changing season begins to affect house plants during September.
Growth may slow as daylight levels fall.
Gradually reduce watering where plants require less moisture.
Do not continue a midsummer watering schedule automatically.
Feeding can also be reduced for plants entering slower winter growth.
House plants that spent summer outdoors should begin returning indoors before nights become too cold.
Before bringing them inside:
Inspect leaves
Check beneath pots
Look for slugs and snails
Check for aphids
Inspect for spider mites
Remove dead foliage
Clean plants and containers before returning them to the house.
Avoid positioning tropical plants immediately beside cold windows or draughty doors.
The lower autumn sun can provide useful light, so reconsider positions that were too bright during midsummer.
September can feel like summer one day and autumn the next.
Warm Days
Periods of warm sunshine are still common.
New planting can dry out surprisingly quickly, so continue checking soil moisture.
Cooler Nights
Night temperatures begin falling noticeably.
Tender plants may slow and tropical plants kept outdoors should be monitored.
Heavy Rain
Autumn rainfall can expose drainage problems.
Clear gutters, gullies and drainage channels regularly.
Strong Winds
The first autumn storms may occur during September.
Check newly planted trees, fences and garden structures after strong winds.
Early Frost
Frost is unusual in many parts of the UK during early September but becomes increasingly possible in colder, northern, inland and exposed areas as the month progresses.
Have protection available for vulnerable plants.
Plants to enjoy in September
Border and rock garden
Rudbeckia
Golden yellow flowers continue providing intense late-season colour.
Echinacea
Coneflowers remain attractive in flower and later produce distinctive seed heads.
Helenium
Warm yellow, orange and red flowers are ideal for late-summer and early-autumn planting.
Aster / Symphyotrichum
Michaelmas daisies begin producing masses of daisy-like flowers in shades of blue, purple, pink and white.
Japanese Anemone
Elegant pink or white flowers are invaluable for late-season borders.
Sedum / Hylotelephium
Large flower heads develop pink, red and bronze tones and attract numerous pollinating insects.
Persicaria
Long flower spikes continue providing colour and structure.
Verbena bonariensis
Tall purple flowers continue floating above surrounding planting.
Dahlia
With regular deadheading, Dahlias can remain spectacular until the first significant frost.
Ornamental Grasses
Miscanthus, Pennisetum, Molinia and other grasses begin becoming increasingly important as flower heads develop and catch lower autumn light.
Trees and shrubs with foliage of interest
Acer palmatum
Some Japanese maples begin showing their first hints of autumn colour.
Cotinus coggygria
Foliage can develop increasingly rich tones as autumn approaches.
Cercis canadensis
Heart-shaped leaves continue providing strong foliage structure.
Fatsia japonica
Evergreen foliage becomes increasingly valuable as herbaceous planting begins to decline.
Euonymus fortunei
Evergreen and variegated forms provide dependable year-round colour.
Heuchera
Bronze, purple, amber and red foliage works particularly well with autumn planting.
Hostas
Hostas can remain attractive during early September before their foliage begins to deteriorate later in autumn.
Ornamental Grasses
Although technically not trees or shrubs, grasses increasingly perform the structural role previously provided by flowering perennials and combine particularly well with woody planting.
Trees with colourful fruit
September is one of the best months for ornamental fruit and berries.
Sorbus – Rowan
Clusters of red, orange, yellow, pink or white berries can provide spectacular displays.
Malus – Crab Apples
Crab apples become increasingly colourful and can remain on trees well into autumn or winter.
Crataegus – Hawthorn
Red haws become prominent and provide an important food source for wildlife.
Pyracantha
Large clusters of red, orange or yellow berries create one of the most dramatic autumn displays.
Cotoneaster
Bright red or orange berries become increasingly noticeable.
Ilex aquifolium – Holly
Holly berries continue developing their characteristic red colour ahead of winter.
Greenhouse plants in flower
Greenhouse Plants in Flower
Greenhouses can continue providing strong colour during September.
Pelargoniums
Pelargoniums may continue flowering freely while temperatures remain warm.
Fuchsias
Many Fuchsias continue producing abundant flowers into early autumn.
Begonias
Begonias can maintain excellent displays under protected conditions.
Streptocarpus
Cape primroses may continue flowering for an extended period.
Abutilon
Bell-shaped flowers can continue while greenhouse temperatures remain suitable.
Bougainvillea
Warm, bright conditions can prolong its display of colourful bracts.
Orchids
Various orchid species and hybrids may flower during September according to their individual growing cycle.
Preparing the Garden for Autumn
September is the month when preparation begins to replace pure summer maintenance.
There is no need to clear the garden simply because autumn is approaching.
Many fading plants have considerable value.
Seed heads provide structure, grasses create movement and berries feed wildlife. Allowing selected plants to remain standing can create a garden that continues to look attractive throughout autumn and winter.
Instead, remove what is genuinely untidy, diseased or obstructive while preserving plants that continue contributing to the garden.
September is also the beginning of one of the best planting periods of the year.
Warm soil and increasing rainfall provide excellent conditions for establishing new trees, shrubs and perennials.
Look carefully at the garden while the memory of summer is still fresh.
Identify gaps in flowering, privacy, shade and structure and use those observations to plan autumn improvements.
A productive September can lay the foundations not only for a better autumn garden, but for a stronger garden next spring and summer.