Taking care of perennials

By John Fulton

[October 19, 2011]  With the change of the seasons upon us, outdoor time is a valuable commodity. We just don't know when the chance to do things will end. Every evening reminds me of this fact, since we don't have daylight until 8:30 every evening anymore. One of the later fall chores is taking care of perennials, but the push may be there to do it as we are finishing up mowing.

Many perennials are better left standing over the winter than cutting them down. There are several reasons for this. In addition to many of the perennials having attractive foliage or seed heads, they offer food resources for birds. Many birds find the seeds of perennials particularly tasty. The stems of perennials also offer a place for some birds to hide during the winter. With some marginally hardy perennials, leaving the stems up for the winter aids in overwintering. The foliage helps to insulate the crowns. Mums seem to benefit a great deal from this practice. Another reason to let stems stand is that if the perennial is a late riser in the spring, the stems will help to mark the spot and prevent any accidental digging in the area that might harm the underground portions of the plant.

Cutting back perennials in the fall may be something you would want to do, especially if you were bothered by foliage diseases. Removing the old foliage would be a positive in this case, as it helps to reduce the amount of disease present to infect next year's foliage. Removing foliage can also be one of pure aesthetics. Some gardeners like to see standing perennials in the winter and others don't.

When perennials are cut down, do so after they have gone dormant. This is usually after the plants have experienced several hard frosts. We aren't there yet this year but will be sometime soon. Cut the plants down to within 2-3 inches of the crown. Cutting too close can result in winter injury on some perennials, due to the fact the buds for next year's growth are right at or above the surface.

Remember, mulches help keep temperature and moisture conditions more stable. Mulching after the ground is frozen will keep mulched plants dormant for a longer period of time. A depth of 2 to 4 inches is sufficient. Materials may be anything, but the best ones will not pack and smother. Oak leaves are great, while silver maple leaves are not. Straw also works well. If you have problems with mulch being blown off the area, you can make a short enclosure of chicken wire, hardware cloth or any other material.

Take advantage of unfrozen ground to provide moisture for all perennials as needed. Rain or wet snow can provide the moisture, but usually the weather is dry enough to have benefit from some added water. Evergreens are particularly sensitive to drying out during the winter months. Evergreens may even be helped by an antidesiccant (such as Wilt-Pruf) applied around Thanksgiving. White pines are among the most prone to drying out.

[By JOHN FULTON, University of Illinois Extension]