Fall arrives, and the perennial flowers have done their work for the year. Leaves drop, blooms wilt and it seems that everything is done. Yet proper perennial care hasn't ended. There's still a lot to do to help your perennial plants survive the winter and be ready to reward you with new growth in spring.
Pruning, Watering and Fertilizing
For those of you who live in southern areas without hard frosts, the garden may continue to need your care throughout the winter. Watering is important if conditions are dry. In northern areas where frost kills most plants, you should continue to water woody ornamentals and broad-leaved evergreens, like holly and rhododendron, until the ground is frozen. Once herbaceous perennials have gone dormant, watering isn't necessary.
Stop most fertilizing around the beginning of September. You don't want to encourage new growth that will be killed by cold weather. Perennial shrubs should have one last fertilization in September just before they go dormant.
If you are going to cover roses with cones for winter protection, only prune them back far enough so that the cone will fit. The same is true if you are going to protect other perennial plants with winter covers. Perennial plants die back from their tips toward the center of the plant during the winter. The dead wood at the tip offers some protection for living tissue further down. The more growth you leave, the more living tissue may survive until spring. Never put on the plant covers until the ground is frozen and day temperatures are below 40 degrees Fahrenheit.
When the hosta have dissolved into piles of wilted leaves and other plants become naked sticks in the garden, the first instinct of many gardeners is to go in and clean up everything. This isn't always the best choice. Most plants are happier going into winter with their dead foliage protecting them. Some plants, like ornamental grasses, bamboo and tall sedums, will provide some winter interest in the garden if the growth is left.
Some perennial flowers and plants may look dead, but their stems have small buds that will start growing in spring. Chopping them off to the ground will leave them struggling to catch up in the spring. The stems of plants trap snow, which helps to mark the spot where they are so that you won't disturb them.
That doesn't mean there's no cleanup to be done. Any plant that had a disease problem, like rust or powdery mildew, should have its dead foliage removed and burned or thrown away. If you don't want the winter interest from ornamental grasses, you can cut them back to a few inches above the ground. Remove tall seed pods or flower stems as well, if winter interest isn't desired. All annual plants that were used as filler should be removed.
Weed your perennial flower beds thoroughly and edge them. If you want to expand your flower beds in spring, lay out the new areas now and remove any existing sod with herbicides or by smothering. Thick layers of newspaper and mulch will do the trick.
Dig up any summer bulbs that are not hardy and store them. Dump out container gardens or plant them in the ground if you want to save perennials in them. You'll want to plant the containers so that the soil level in the container is the same height as the surrounding soil. Leaving containers above ground will let the soil freeze and kill the plants.
If you must, you can carefully remove dead foliage from many perennial plants after they have gone dormant. Don't yank out leaves; cut them off or you may uproot or damage the plant. Some plants, like heuchera, dianthus, thyme, ajuga and lamium, have leaves that remain green through the winter. These are best left alone.
Carefully trim off semi-woody perennial plants, like chrysanthemums, to about six inches above ground to avoid damage to buds growing near stem bases. These plants may actually survive better if you do not trim them until spring.
Leave lavender, rosemary, sage, creeping sedums, clematis and other vines until spring. Also leave shrub and landscape rose pruning until spring. You can cut buddleias right to the ground as they bloom better and look nicer when they come back from the roots. For other woody perennials, leave any pruning until spring. Some varieties will only bloom on existing growth, so pruning could wind up costing you a full complement of spring blooms.
Transplanting and Planting
Early fall is a good time to move perennials to a new site, but it is not the best time to divide them. Try to move plants so that they have at least six weeks before a hard frost or freeze to establish new roots. Be sure to keep them watered if the weather is dry.
If you need to order flowers, remember that most perennials are not sold in the fall. Oriental lilies and some hybrid lilies do better when planted in fall. Some woody perennials, such as hydrangeas and viburnums, are often sold in the fall.
If you want spring flowering bulbs like tulips, alliums, daffodils and crocus, fall is the time to plant them. Try to get them in the ground six weeks before the first freeze, definitely before the ground freezes solid.
Mulching and Winter Protection
Mulch for winter protection is put on after the ground freezes. It is meant to keep the ground from freezing and thawing, which pushes plants out of the ground and exposes the roots to killing cold. In some cases mulch is also used to protect the crowns of plants from the cold.
Mulch can be wood chips, shredded leaves, pine needles, straw or any other light, non-matting material. Leaves other than oak leaves will form a thick mat that can smother plants unless they are chopped before applying.
A ring of wire holding mulch or special insulating cones can be used to protect plants that aren't quite winter hardy in your zone. Put these on after the ground freezes.
Fall perennial care needs vary from zone to zone. If you're in the South and don't face freezing conditions all winter, your plants may need less attention. In the far North, mulching is almost always necessary.
Remember, most perennials will survive a normal winter without a lot of effort on your part. But if you want those specimen plants that get everyone in the neighborhood talking, a little attention in fall will go a long way toward robust growth and better blooms in spring.
Now I am sure you are asking, "Why would I want to know about Joe Pye Weeds" Well, it is a wild flower that is also known as a 'Trumpet weed' or 'Queen of the Meadow'. It is North American native perennial herb from southern Canada to Florida and from there west to Texas.
For long-lasting color in the garden, there are few perennial plants easier to grow than coreopsis. Coreopsis loves sunny, hot conditions and will bloom its heart out through the middle of the hottest summers. The bright gold of native species of coreopsis has been altered by plant breeders into several muted and pastel shades that make coreopsis fit into any garden color scheme.