When herbaceous perennials finish flowering for the season, we naturally want to cut them back, often to the ground. This year you may want to leave some intact for winter interest. Sure, they may be brown but brown contrasts with white snow.
Herbaceous plants are those with leaves and non-woody stems. Herbaceous perennials are those that die back to the ground every year but grow back the next spring. Their roots stay alive, though dormant. Hostas are good examples. Other perennials are woody shrubs like lilacs and viburnums.
Some perennials grow so low that they won’t be seen above the snow. Others, however, grow taller so they will protrude out of the snow banks. Before the snow flies herbaceous perennials that have died back may not be particularly attractive. , After a snow fall, these plants can provide a nice break from the endless sea of white outside our windows. As the photo shows, even brown plants can add nice texture to a winter scene.
Before cutting back perennials, I suggest that you look at them not as dead pants but rather whether they can add winter interest to your otherwise monochromatic (white) yard. Leave those that will show above the snow and cut and compost the rest.
There are a few winter blooming perennials that will grow in the northeast. Pansies are perhaps the best known but hellebores, snowdrops and some varieties of phlox will also add color to your landscape on those drab days of winter.
Woody perennials (trees and shrubs) won’t die back to the ground but the deciduous plants lose their leaves and go dormant in winter. Only a few, witch hazel for example, may flower in winter. Others add winter interest in other ways. Dogwood shrubs show off their red branches in winter while holly shrubs display their red berries. Holly plants are dioecious, which means male and female flowers are on separate plants. So you need a male holly plant nearby to have red berries on the female plants. Monoecious plants have both flowers on a single plant.
Don’t prune flowering shrubs like lilacs in the fall. They’ve already set their flower buds for next spring, and you may cut them off when pruning. Most shrubs do flower in spring but a few flower later in the season on new branches. Buddleia (butterfly bush) is an example. The rule of thumb is to wait to prune all woody plants until after they are finished flowering.
Most of our perennials are evergreen, so do not get cut back until after winter. Those that get damaged by the frost do not get cut back right away (unless they are just too unsightly to leave) because pruning them back stimulates premature growth that is even more sensitive to subsequent frost. Besides, the damaged foliage protects provides a bit of insulation just in case there is another frost. They might be protected under snow, but it does not snow here.