This post is a feature from Vern Goers Greenhouse's on-staff horticulturist Dan Kosta. In case you missed his great workshops at the Fall Festival, here are his main points to keep in mind when getting ready for winter.
Annuals: Most annuals, such as impatiens, marigolds, and sweet potato vine, should simply be discarded at this time. A few annuals are more able to withstand the colder temperatures of early and mid fall. Among these are geraniums, dianthus, salvia, petunias, and dusty miller. These plants are actually perennials in somewhat warmer climates but they may not survive through the winter in our region. You may notice that their flower colors become even more intense and vibrant at this time of year.
One other group of annuals actually prefers the cooler temperatures and should be planted at this time. These would be pansies, alyssum, ornamental forms of kale and cabbage, and Swiss chard
Perennials: Most perennials require little care at this time. You may wish to clean up the perennial garden or border by cutting down the dead stems and foliage once frost has turned the yellow. For some perennials you might leave seed heads standing as decorative accents or for food for birds. Among these are Echinacea, Rudbeckia, and
Newly or recently planted perennials should be mulched after the soil freezes in late fall. This is actually the best time of year to plant perennials that have been growing in containers. It is not advisable to dig and move or divide existing perennials. If there are any that do not get planted they can be stood in their pots on the ground in a protected area and buried in a generous-sized mound of mulch.
Ornamental Grasses: These plants should be left standing for the winter. They are their most decorative during the fall and winter seasons. Remove the browned foliage and seed heads in early spring.
Roses: It is best to not prune the roses at this time. Remove all shed foliage from the area, especially if there have been foliage diseases on the plants. Remove spent flowers from all but rugosa types. All roses except Knock Out or rugosa types should be mounded with mulch once the ground freezes.
Lawns: Apply 2 or more applications of a good fall fertilizer. Try to find one with higher amounts of phosphorus and potash and lower amounts of nitrogen.
Shrubs and Vines - Mulch newly planted shrubs and vines. Do not prune at this time.
Containers - It is best to empty containers and store them upside down and kept dry until spring. Any winter-hardy plants may be removed and planted in the garden. Plastic, metal, or stoneware containers may be left outdoors. Terra-cotta is best brought indoors.
General Care - It is important to water the garden if there isn’t sufficient rainfall. Do not apply fertilizers except on lawns