By Jim Klett, Colorado State University Cooperative Extension Specialist, Landscape Plants
Perennial borders should be tidied up when growth ceases in the fall. Continue flower removal as necessary until cold kills the plants to the ground. After perennial foliage dies down to the ground, you can remove it, though you might want to leave ornamental grasses until late winter for the texture they provide in the landscape.
After the ground freezes, mulch perennials to prevent alternate freezing and thawing of soil, which can tear roots and lift crowns above soil levels. This can result in plant death. Use a light mulch that will not smother plants, such as pine, spruce or fir branches from Christmas trees, leaves or hay. Remove the mulch gradually in the spring.
Photographs courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010