With November half gone, the yard and garden activity agenda gets light. One area of focus for late November is protecting landscape plants from fluctuating conditions winter may bring. This includes perennials, strawberries, roses, and younger trees.
Winter mulches are intended to prevent alternating freezing and thawing of uncovered soil surfaces, which can be destructive to roots and lower stem tissue of many herbaceous perennial plants. If significant snow cover develops by early December and remains in place until spring thaw, mulching will not be needed. Since we cannot depend on protection of snow cover, it is suggested that winter mulch be applied in extremely late fall.
There are a few parameters to applying winter mulch correctly. First, perennials being covered should be dormant. Second, ideally the ground would start to freeze. Late fall conditions vary across Wisconsin each year, so it is best to see what happens and adjust timing accordingly, but ballpark timing is about Thanksgiving. Straw, marsh hay, and evergreen boughs make ideal winter mulch materials. If using leaves, shredding them first helps prevent them from matting down and creating excessively dense layers. Unless infected with disease, allowing foliage of most perennials to be left standing all winter is beneficial.
Roses can be damaged by drying harsh winter winds, and rose cones are popular to provide protection. Make sure roses are dormant before covering them, so late November is usually about time to put cones on. Cones should have ventilation at the top to reduce chances of conditions getting too warm and humid inside. Only prune enough this fall to allow roses to be covered, then address additional pruning in spring based on winter dieback.
Trees with smooth bark, particularly younger landscape and fruit trees, are prone to damage from fluctuating trunk temperatures, especially in late winter. On clear days, bark exposed to the afternoon sun often significantly heats up, only to rapidly cool off at night as air temperatures drop into the teens or single digits. Sunscald injury results, creating damaged areas of loose, sunken, splitting, or missing bark.
Help prevent these types of damage by wrapping tree trunks now. Use light colored tree wrap, starting at the bottom and working up to the first set of branches, creating an overlapping shingle effect to shed water. Commercially available plastic tree guards can be used for this same purpose. In addition, they can help reduce trunk damage from deer and rabbits over the course of the winter.
Finally, continue to monitor soil moisture conditions around trees, in particular conifers and broadleaf evergreens, for the balance of fall, and provide water if needed.
By Bruce Spangenberg, Horticulture Outreach Specialist, UW-Madison Division of Extension
