Continue to deadhead flowering plants.
Cut back flowered perennials and herbs to encourage a second flush.
Stake tall late-flowering perennials to stop them being blown over.
Divide any overgrown or tired looking clumps of alpines and herbaceous perennials.
Plant new perennials, shrubs and trees.
Plant out spring-flowering biennials such as viola, foxglove or wallflowers.
Take cuttings of tender perennials and herbs.
Divide herbs and pot clumps for winter use in the kitchen.
Sow sweet peas in a cold frame for early summer blooms next year.
Sow other hardy annuals in situ.
Bring inside any tender perennials, such as Fuchsia and Abutilon before frosts cause damage.
Wait until first frosts before lifting the tubers or rhizomes.
Buy or order spring-flowering bulbs. For the best results plant daffodils Narcissi by mid-September and tulips in November.
Continue collecting and storing seed from perennials still forming seed heads.
Treat perennial weeds which are still vulnerable to weedkiller.

Trees and shrubs.

Plant and transplant tress and shrubs.
Take semi-ripe cuttings of evergreen shrubs such as Cistus, Ceanothus and Viburnum.
Take hardwood cuttings of roses, choosing well-ripened, healthy shoots.
Trim evergreen topiary and shrubs.

Lawns.

Mow less frequently, and raise the height of cut as the growth rate of the grass slows down.
Last opportunity to use a lawn weedkiller to control perennial weeds such as daises and buttercups.
Apply an high potassium autumn lawn feed after scarifying and aerating but before applying a top dressing.
Create a new lawn, or rectify summer damage with turf or seed.