General maintenance
Do not feed plants this late in the season, as they are no longer growing the nutrients may be washed into rivers and streams by winter rain. Apply an autumn mulch to protect plants that are borderline hardy such as Agapanthus (African Lily), Kniphofia (Red Hot Poker), and Phygelius (Cape Fuchsia). The plants’ own leaves, e.g. Kniphofia can be tied up and used as protection for the crowns underneath. Clay soils can be more workable in autumn, as they are no longer baked hard, but not yet sodden and sticky with winter wet, mulching will help to improve and maintain soil structureMake sure that you have not forgotten any of your tender plants and bulbs - they need to be brought inside or into a heated greenhouse over the winter. Protect alpines from the wet, if you have not done so already.
Large tubs that are at risk of cracking in the frost should be covered with bubble wrap, hessian or fleece, to insulate them over the winter. Raise patio containers onto feet or bricks to avoid them sitting in the winter wet.
Tidy up leaves from around borders. They can be added to the compost heap, or placed in separate bins to make leaf mould. Leaf mould makes an excellent soil improver, and can also be used as a seed-sowing medium. Dig new flower beds as the weather allows. Don't work on them when it's very wet, as walking on sodden soil can cause compaction. In mild weather, weeds will still appear. Hoe regularly to keep them in check. Now can be a good time to dig up perennial weeds with long tap roots, such as dandelions and mallow, from newly cultivated areas. Weedkillers are only effective in mild areas, so if you missed the spring and early autumn application periods, you may still be able to spray in warm regions of the UK. Products containing diquat will not kill weed roots but remove foliage and clear weeds even in cool, dull, wet weather. They are non-selective, however, and other plants must be protected.
Pest and disease watch
Watch out for downy mildew and black spot on winter pansies. Check chrysanthemums regularly for signs of white rust. Look out for crown rot and brown rots (sclerotinia) on died down perennials, especially if you are on a clay or poorly-drained soil. Be aware that many diseases will overwinter in the soil, or on plant debris. Antirrhinum rust and Delphinium black blotch, as well as sclerotinia (stem rot), will lay dormant and re-infect plants when they come up the following year. It may be necessary to replant new specimens in another place if the problem is severe. Gather up fallen leaves from around the base of rose bushes which suffered from blackspot or rust this summer, to reduce the chance of infection next year. Digging the soil, especially bare patches or newly cultivated land, will expose pest larvae and eggs to birds and frosts, as well as clearing weeds and improving soil structure. Don’t leave soil uncovered for too long, however, as it runs the risk of erosion and washing away of valuable nutrients. Black polythene sheeting will protect it in the absence of planting or mulch.