Save the beautiful dahlias for next year's garden by trimming off the tops, then, using a spading fork, digging up the roots. Gently remove most of the soil and place them on a piece of newspaper in a dry space. Once dry, gently remove the remaining soil, wrap loosely in blister padding, put in a box, and store in a frost-free garage or other storage area.
Consider Bulbs for Wet Areas
Although most spring-flowering bulbs need well-drained soil, there are certain ones that do well in wet places. If you have an area with soggy soil, such as along a stream, near a water garden or in a rain garden, try summer snowflake (Leucojum aestivum), guinea flower (Fritillaria meleagris), and camassia, including C. cusickii, C. quamash, and C. leichtlinii.
Plan for Rhubarb and Asparagus
Rhubarb and asparagus and both easy-to-grow foods that are long-lived. They are usually planted in early spring, when it's often difficult to prepare the bed for them. It's much easier to deeply dig an area for them at this time of year. Be sure to work in plenty of compost or composted manure as well as a complete fertilizer. Then you can quickly and easily plant them next spring.
Make a Fall Bouquet
Although many of the flowers in the garden are gone or past their prime, it's still possible to have dramatic bouquets at this time of year. Start with a few branches of colorful fall foliage, such as dogwood, sassafras or sugar maple. Fill in with the seedheads of ornamental grasses and fall flowers like goldenrod, purple asters, or caryopteris. Add some branches of berries, such as the brilliant purple beautyberry (Callicarpa).
Spare Some Perennials
Garden clean-up is well underway. Cleaning up the garden now is a great way to get a head-start on next year, but don't get overzealous. Spare some of your perennials now in order to both have some winter appeal to the garden and provide seeds and cover for the birds. Some of the ones to consider saving include ornamental grasses, Echinacea, Rudbeckia, Sedum, and Astilbe.