At the time of writing this we have just had a lovely Indian Summer and looking through last year’s write up I said a similar thing. We must now watch out for frosts, which can bring a sudden end to fading summer displays, and bring in tender plants and crops under cover.
As late perennials finish flowering cut down the top growth, weed and fork between the plants. Cut late summer flowering clematis right down to soil level.  Plant new herbaceous perennials and dig up, divide and replant any that are overcrowded.  Plant lilies, ornamental onions and lily-of-the-valley for forcing.    Plant polyanthus, sweet William, wallflowers, foxgloves, forget-me-nots and Canterbury bells.  Mulch established plants with peat or leaf mould.  Penstemons are best left as-is until the spring, when they can be cut back further. Lift and store dahlias, cannas and tuberous bedding begonias that have been hit by the first frosts. Take root cuttings of oriental Poppies.  Plant tulip bulbs this month to make a lovely spring display and it is not too late to put in your daffs.
Plant out bare rooted roses and pick up and burn any fallen leaves.  Heel in roses that cannot be planted straight away. Make sure climbing roses are tied in.
Get the soil ready for spring sowing.  Asparagus beds should be dressed with rotten manure and prepare new asparagus beds for planting up in the spring. Plenty of organic matter and grit will help to improve drainage to the level required by asparagus.
Beetroot and carrots should be lifted and prepared for the freezer. Celery and leeks require earthing up. Parsnips may need covering.  Spinach will continue to crop as it is thinned.
Stake Brussels sprout plants.  Protect cauliflower curds by bending the leaves over them.  Lift and store in sand artichokes.  Sow broad beans and early peas under cloches.
Plant onion sets and garlic.  Apparently a recently arrived onion pest is likely to spread.  Allium leaf miner attacks leeks, onions, chives, garlic and shallots and may also affect ornamental species and cultivars of Allium.  Gardeners should be on the lookout for signs of the pest.  These include characteristic white lines of puncture marks in the leaves from feeding adult females, and stem and bulb damage caused by burrowing larvae.  Ultimately, plants rot from secondary infections of bacteria and fungi.  There are no effective insecticides available to home gardeners against the pest.  It has been suggested that overwintering onions currently in the ground should be protected with horticultural fleece by early March when the fly starts to lay its eggs.  Adults are active between March – April and October – November.  
Start winter pruning of established, open-grown apple and pear trees (not cordons, espaliers, pyramids or fans) as soon as the leaves have fallen.  This is the month to plant Fruit trees.  You can if you wish spray trees with a suitable wash.  Do not prune plums, damsons, gages, apricots, nectarines, cherries.  These are best pruned from April to June.
Currants and Gooseberries should be planted, figs will need thinning and new Strawberry plants should have some manure spread between the rows.   
Rake the lawn with a wire toothed rake to remove dead grass if you have not already done so. Spike the lawn to improve drainage.  Apply an autumn feed.