Many of the plants in our gardens can benefit from some protection from the harsh Wisconsin winters. In particular, extra care should be given towards Zone 5 plants, which are marginally hardy in the Lake Country area of Wisconsin (learn about hardiness zones). Most winterization should be performed after the ground is frozen for the winter. Mulching or otherwise covering plants too early can stop growth prematurely and create warm, moist air pockets preferred by mold and rodents.
Mark lawn and garden edges near driveways and walkways to guide snow removal and prevent snowplow damage. Avoid the use of salt, which can damage or kill plants. Instead, try using sand, gravel or kitty litter to increase traction on ice or snow.
Young trees should be protected from damage from hungry deer and rodents. A wire mesh tree wrap can keep the deer away. Some trees benefit from a late-season fertilizer. Evergreens should be well-watered to prevent damage from excess moisture loss during the coldest, driest days.
Some of the less-hardy shrubs, such as roses, boxwoods, azaelas, and hydrangeas need a little extra protection from the harsh Wisconsin winters.
There are several methods of protecting shrubs, especially roses, in the winter. The preferred method of winterization is the use of a rose collar. A rose collar is a mesh like collar that is placed around the rose. The area within the rose collar is then filled with compost or mulch. With this method, the rose is not pruned back until spring. A rose cone is a commonly used method, although not the preferred. After the first frost, gently bend or conservatively prune the rose canes to fit under the cone. Punch holes in the rose cone for ventilation. Place three stones on the lip of the rose cone to secure it to the ground.
Evergreen shrubs can be sprayed with Wilt-Pruf Plant Protector to prevent excess moisture loss during the winter. Boxwoods can be wrapped in burlap or in Fleece Coats by Bosmere, reusable, easy-to-use boxwood bags.
Any less hardy perennial (e.g. butterfly bush) should be covered with 6-8 inches of mounded mulch, compost, or pine boughs. It is not necessary to cut back most perennials, especially the less hardy, as the remaining plant material can help insulate the plants over winter. Hostas and other perennials with wetter, denser foliage may be cut back to about 6 inches above the soil. Any plant that is still green, such as sedum may be left as is.
Perennial herbs are also not cut back in the fall. Give them a good drink before the ground freezes. A top dressing of compost and manure should be applied and the pine boughs can be used to protect the plants. Tender herbs such as basil, parsley, rosemary, and lemon verbena can be brought into the home for the winter. Make the move gradually with a stop on the porch or in the shade. The transition should be complete before the furnace goes on in the fall. Thoroughly inspect the plants for insects to avoid contaminating your indoor plants.
See our separate article Water Garden Winterization
Plants are not the only things in your garden that can be damaged in the winter. Don’t forget to properly clean and store your garden tools and accessories for the winter. Empty, clean, or otherwise winterize any water-holding container, such as fountains, bird baths, or rain barrels. Finally, clean, winterize, and store your garden tools after you are finished with your last cleanup for the year. It is especially important to remember to winterize power tools, which could otherwise be damaged.