Most gardeners are anxious to ready spring flower beds and borders for summer blooms---you can almost feel the warm winds beginning to blow and the earth warming beneath the sunshine of longer days. Autumn cleanup is a thankless task---a race against shorter days and raw winds to do away with decay that will be covered by snow and ice in just a month or two. The fall garden, though, is where next summer's triumph begins. Those who neglect maintenance as the leaves fall will have to work twice as hard next spring.
Step 1 Rake up leaves and other debris from the garden and remove the summer mulch layer. Set this material aside---it can go into the compost heap later. As you sweep out the debris, deadhead flowering plants to collect seeds to sow now or next spring and pull the last weeds (yes, there will still be weeds).
Step 2 Pull or dig up annuals such as marigolds and petunias by the roots. Shake the dirt off the roots and add it to the compost or return it to the bed---it's been conditioned all summer long and is the ultimate in lightweight soil. Deposit plants and other healthy vegetation into the compost bin. I know this is going on in the flower beds all over. I finish lots of the plants for the Mason City beautification program in Mason City, and I know that is what the Gardeners of North Iowa are doing soon...cleaning up the old plants so we can plant in May.
Step 3 Dig around perennials that have spread beyond their spaces, and discard or pot up extras to share. Every few years, depending on the plant, dig up clumps that have grown too thick or stopped blooming and split clumps or separate tubers, rhizomes and bulbs to make more plants. Add compost as you plant new divisions, and mark the area to avoid digging up the new plants as you work. Good time to divide perennials, but the rule of thumb if the perennial blooms in the spring, then divide, move in the fall. Opposite seasons that it blooms. Summer and fall blooming perennials would work now.
Step 4 Cultivate and plant biennial seeds like hollyhock, foxglove, Canterbury bells or violets; many wildflowers; and spring-and-early-summer-flowering bulbs like hyacinths, daffodils, tulips and lilies. Mark areas where you have planted seeds and bulbs to avoid disturbing them later. Tulips and daffodils should be up by now. Lilies I don't know so be careful with the cultivating of the garden with new stuff.
Step 5 Trim the foliage on perennial flowers back to minimize shelter for rodents and garden pests looking for winter homes. Most foliage can be cut to the ground, but some, like roses, should not be cut back but pruned in the spring. Keep an eye out for snails and slugs---don't add them to the compost heap. Rake the garden a final time to remove plant material.
Step 6 Add manure and other soil amendments, such as compost or peat moss (lime or sulfur to correct pH) after the first hard freeze. Turn the soil to work in nutrients and expose all the pests that have been burrowing down into the soil for protection. Let them freeze for a night or two, then begin mounding the roses and mulching the garden with 2 to 3 inches of fresh mulch. I am afraid I would tell you to do this after the ground warms up. I have found with experience when I mulch too soon the ground stayed cool all season long and the plants didn't seem to grow that well.
taken from http://www.gardenguides.com/67976-clean-out-flower-beds.html
Till next time, this is Becky Litterer, Becky's Greenhouse, Dougherty, Iowa