Winter Care for Pernnials
Diane Relf
Virginia Tech

The approach you prefer for preparing your perennial border for the winter may have more to do with your personality than with the needs of the plants. Gardeners with time and energy or a strong sense of order may take advantage of late autumn to clean the beds of old stems and dense mats of foliage. This can be valuable not only from an aesthetic perspective, but also to reduce the potential for insects and diseases to be carried from one year to the next. After a proper clean-up day, the tidy beds are freed of foliage, the compost pile is full, and mulch has been carefully spread for the season.   

Untidy Flower Beds Look Good, Too   

However, I found over the years that there is something appealing about an untidy perennial bed where the deep-rust seed heads of Autumn Joy sedum contrast to the snow, and collapsed foliage adds texture as well as self-made mulch. I acknowledge that the younger self I carry in my head sees this shift in attitude as laziness. But I have control of that situation and am quite comfortable with the new-found freedom to admire rather than constantly alter my surroundings. One added benefit of this relaxed attitude is that seed heads attract great flocks of goldfinches and other birds in the fall and winter.   

Mulching Should Wait Until Ground Freezes   

In addition, this approach relieves me of some concern for the timing of all my work. While it is appropriate to do some cleaning after the first heavy frost, mulching should wait until the ground is frozen several inches deep. The purpose of the mulch is, in fact, to keep the ground frozen and the plants cold. The biggest winter damage to perennials is the freezing and thawing of the soil that causes shallow-rooted plants to heave from the ground much as rocks are moved to the surface in some areas.   

Mulch Protects Against Damage from Warm and Freezing Temperatures   

Another cause of damage is growth that is stimulated during warm spells, and then freezes when the temperatures drop again. Loose, shading mulch, such as branches from a Christmas tree or a thin layer of pine needles, is ideal to offer the needed protection. Heavy, dense mulches tend to cause rotting. Mulches applied too early can actually aggravate problems by delaying the dormancy of plants.   

So, I will take care of the maintenance tasks that need to be done to keep my plants healthy and vigorous, but will continue to enjoy the aesthetics and visitors an untidy perennial bed can bring.   

 Dr. Diane Relf is an environmental horticulturist with Virginia Cooperative Extension and a member of the faculty of Virginia Tech.