Garden jobs for September

General garden maintenance

  • Keep deadheading plants all around the garden to prolong the flowering season.
  • Give evergreen hedges their final trim of the year.
  • Keep Camellias, Azaleas and Rhododendrons watered regularly as their flower buds continue to develop. If they go without water, the buds may drop in spring or fail to open. These ericaceous (acid-loving) plants should ideally be watered with rainwater but are fine to be watered with tap water if rainwater isn’t available. Note that over a long period ericaceous plants watered with hard water will start showing signs of chlorosis (yellowing of the leaves). Help to avoid this by mulching with ericaceous compost.
  • Herbaceous perennials which are too big in their allotted space or which look tired, can be divided and replanted before they die down. Water them in well and mulch around the plant.
  • Apply a good layer of compost or manure as a mulch around established trees and shrubs, including fruit trees, roses and wisteria. One aim of applying mulch is to trap in moisture so make sure you have watered dry ground first.
  • Start to clear away garden debris from beds and borders and from around containers.
  • Keep up general maintenance around the garden, removing dead and dying leaves from plants, pulling up weeds and generally cleaning to help prevent pests and diseases overwintering.
  • Sweep fallen leaves from lawns and paths.
  • Cover ponds with net to prevent leaves falling in and affecting water quality. Nets also protect fish from herons and other predators.
  • Get your compost bin ready for the leaves and pruning that you will be collecting over the next couple of months. Vegetable gardens will generate a lot of compostable material too.

Container gardening

  • Summer bedding containers can be prolonged by deadheading and feeding with a high potassium fertiliser such as tomato feed.
  • Containers can be replanted with a range of interesting leafy plants such as grasses, ferns, heuchera and small evergreen shrubs, as well as flowering pansies, viola, cyclamen and others.
  • If you are using a container which has been used for summer planting, refresh or replace the compost.
  • Pop some dwarf spring bulbs such as iris, crocus or dwarf narcissi under your autumn/winter container plants - it takes no time and will brighten the containers early next year.
  • For more permanent container planting of specimen plants and shrubs ask yourself whether you need to repot. This might be into a bigger pot or into the same pot by lifting the plant, pruning the roots and repotting with fresh compost. Know your plant and its requirements before doing this.
  • Think about planting a potful of bulbs - known as a bulb lasagne - to enjoy months of different colour from January right through to April or May. Larger bulbs such as tulips go at the bottom, narcissi or hyacinth at the mid-level and smaller bulbs such as dwarf iris or crocus at the top. You can buy bulb combinations in packs, or make up your own mix.


  • Prune late summer flowering shrubs when the flowers have finished, including climbing and rambling roses.
  • Leave flower heads on macrophylla and lacecap hydrangeas to protect young developing buds below. They are best pruned in early to late spring.
  • Once lavender flowers have faded, cut the plants back with secateurs within the green growth, not into brown wood. Doing this each year will maintain neat, compact plants and encourage more side shoots to grow.


  • Fill gaps in borders with late flowering perennials such as Sedum, Rudbeckia, Penstemon, Anemone, Salvia, ornamental grasses and much more.
  • As mentioned earlier, autumn is a perfect time to plant new shrubs, trees and perennials - the ground is warm and the roots have time to get established before getting off to a good start next spring.
  • Start planting spring-flowering bulbs now in beds or containers. Most bulbs can be planted from late summer into the autumn, leaving tulips until later. Bulbs should be planted at the right depth - general rule is a depth equivalent to two to three times their own height. The packs give all the information you need - flowering time, height and colour, and planting distance and depth.

Watering and feeding

  • Ease up on feeding shrubs and trees with general fertilisers in containers, because soft new growth would be damaged in the winter months.
  • Keep watering plants in dry spells to reduce stress and the risk of disease such as powdery mildew.

Fruit and Vegetables

  • Remove fallen fruit from around trees and shrubs before it rots.
  • Plant vegetables such as cabbage, cauliflower, broccoli, kale and more to enjoy through winter and spring.
  • Fix grease bands round the trunks of apple trees to trap the wingless female winter moths as they try to climb the trunk to lay their eggs, which would turn into bud eating caterpillars.
  • Use netting to protect leafy vegetables from pigeons.
  • Root vegetables can be lifted and stored, but leave parsnips and swedes in the ground to be frosted as this improves their flavour.
  • Pinch out the top of cordon tomatoes to concentrate energy into ripening fruits. Remove any yellowing leaves and leaves which are covering the fruit. This will increase air circulation and help to reduce the risk of grey mould. Water regularly to avoid the fruit splitting.


  • ‘Tender’ herbs will continue to grow outside until the first frosts, and evergreens like rosemary, thyme and sage will remain above ground to use through to next spring.
  • Pot up herbs such as parsley, mint and basil for the kitchen windowsill to enjoy over the winter.


  • It’s not necessary to water your lawn. Lawns which have browned over the summer will soon show green growth with a few days of rain.
  • As the weather begins to cool, the lawn will benefit from an autumn work over. It’s worth spending some time and elbow grease in the next couple of months:
    • Remove old “thatch” (dead grass) and moss – use a springy rake to clear the congestion that has built up over the growing season.
    • Aerate – to improve drainage and help protect against a buildup of moss – use an aerator designed specifically for the job, or a fork.
    • Fertilise – a thin layer of lawn dressing ****(a combination of top soil, sand and fertilisers) or horticultural sand, should be raked or brushed to fill the holes created by aerating. This will improve drainage and avoid winter waterlogging, especially in heavy clay soils.
  • September is an excellent time to lay a new lawn with turf, or from seed. Take time to prepare the ground beforehand, giving it a good foundation.
  • Use a lawn weed killer to control perennial weeds before the weather cools.

Pests and disease

  • Box tree moth is causing problems for many of our customers. If you use an insecticide, follow the instructions carefully and use it in the evening when beneficial insects aren’t around. Use a box tree moth trap and ensure that the plants are as healthy as possible by using a fertiliser such as Top Buxus.
  • Keep a continued vigil against slugs and snails, and make sure you don’t leave places where they can settle in for the autumn and winter months.
  • Check for vine weevil in containers. Treat with appropriate chemicals or nematodes.


  • Keep feeders topped up for the birds and leave water out for them too. If we look after bird life with food and water, they’ll help us in return by eating unwanted insects in the garden.
  • If thinning out plants in ponds, leave the debris at the side of the pond overnight so that wildlife can find its way back to the water.