Cutting Back Perennials in the Fall

Cleaning up the garden in the fall can be a bit confusing, especially when it comes to cutting back perennials. Should you leave them alone or cut them back as soon as they fade? The answer, of course, depends on the plant.

When to Leave Them Alone

In general, as long as your perennials look good, leave them alone. Sure, some may die back after the first heavy frost, but others will remain standing and add interest to the garden all winter long.

Advantages of leaving dried seed heads and foliage of healthy plants intact until next spring:

• Aesthetic appeal. Ornamental grasses and evergreens, for example, look great in the winter.
• Provides food and shelter for native animals and birds.
• Beneficial insects overwinter in plant debris.
• In cold climates, dead plant foliage traps leaves and snow (insulation and moisture). This helps improve its chances for survival over winter while helping to protect other garden plants.
• Intact plants serve as a reminder of where your plants are when it comes time to add plants in the spring.

When to Cut Them Back

Certain plants benefit from being cut back in the fall. Rarely is this important aesthetically, but from a sanitary standpoint, it can make or break your next growing season. If insects or diseases attacked some of your perennials this year, the best thing to do is cut them back. This reduces the chances of carrying over attacks to the next season and eliminates over-wintering sites for rodents or harmful insects.

Make sure you dispose of damaged plant debris in the garbage and not the compost pile. Most perennials can be safely cut back to within a couple of inches of the ground.

Visibly damaged or infested foliage should be removed as soon as possible, but if you are cutting back foliage as a preventive measure, wait until after several hard frosts have killed back the tops. Depending on the plants, hand pruners, hedge clippers, or even scissors will work fine, just make sure the cutting edges are sharp.

Advantages to cutting your perennials back in the fall:

• Gets rid of plant debris damaged by insects or disease.
• Eliminates places for rodents or harmful insects to spend the winter.
• Gives the garden with a neat, clean appearance.
• Saves time in the spring in zones with short growing seasons (It's still a good idea to save a stem or two to trap leaves and snow.)

Apply Mulch After Cutting

If you decide to cut back your perennials in the fall, take the opportunity to apply some mulch before winter. With the stems and foliage gone from your plants, you will have plenty of room to maneuver. Applying mulch will help your perennials conserve moisture going into the winter, and protect the roots and crowns from cold damage and frost heaving.