To Cut Back or Not Cut Back...
That Is the Question

Barbara Mrgich
Adams County Master Gardener

Mr. Jack Frost comes silently upon your garden in the early morning hours, and when daylight comes, you see sad, browned foliage and drooping flowers. What do you do next?

The official answer to a million gardening questions is, "It depends", and this is one of those times. First you have considerations to keep in mind. If the plant is an annual, and now it looks ugly, pull it out and and throw it in the compost bin.

If the plant is a native perennial, it most likely offers benefits to birds and beneficial insects, so it's a good idea to let it stand. Overwintering birds rely on eating from the seedheads of dried perennials. They also use the protection of trees, shrubs, plant stubs, and ground covers throughout the winter. They forage in the leaves and debris on the garden floor for insects to eat, and, in addition to the seedheads, they enjoy the berries and fruit that many natives have to offer.

Native plants host beneficial insects that may be hiding in or near them for the winter. For example, one of our Pennsylvania resident butterflies is the Viceroy which is a Monarch look-alike. The tiny Viceroy caterpillar will roll itself in a leaf from its host plant then drop with it to the ground where it will stay for the winter. If you meticulously rake those leaves for a clean garden floor, you will be disposing of those future butterflies.

Insects tend to lay their eggs and winter over, on, or near the plants they like to eat. The vast majority of insects are considered beneficial because they eat other insects while they, themselves, are eaten and provide nourishment for birds and other animals. The small percentage of the insects that are pests seem to prefer our vegetable gardens, orchards, and agricultural fields where they spend their lives destroying our crops. Hopefully, all this explains why you want to carefully clean plant debris from your vegetable garden, but leave as much as possible in your ornamental garden. One exception to that rule concerns our beloved Mr. Slug, who eats and shreds your hosta leaves. Clean up those leaves as soon as the frost takes them because they harbor the slug eggs which will hatch and ruin next year's hostas.

Here is a concept to keep in mind before you start cutting back plants. Every plant will send the energy from its roots to its flowers, fruits and foliage to produce the beautiful garden that you love. At the end of the season, that energy will return to the roots for the winter keeping the plant strong for re-emergence in the spring. If you cut those plant tops off too soon, the plant loses its chance to reclaim that energy. So don't be in a big hurry to rush out there and cut plants back.

Cannas and Dahlias are two popular garden specimens which are not hardy in our area, and some people worry that they will die if hit by the frost. You should actually wait for a couple of frosts before digging them, until the energy from the dying foliage has a chance to return to the tubers. Then dig them and store them properly for the winter.

As a master gardener, people ask me how low they should cut off their perennials. Actually, once those stems are dead, and the plant has gone dormant, it doesn't matter to the plant where you cut them, but there are a couple of reasons to leave about a 6 - 8 inch stub. First, it will help protect the crown of the plant from the cold during the winter. Leaves get caught in those stubs and help insulate the crown. Secondly, that stub will stand firm to remind you exactly where that plant is located when you are looking to dig a hole for something else in early April!

Cutting back shrubs is a very different story. Never prune or cut back any shrub in the fall. Pruning encourages growth, and new tender shoots promoted by your pruning, will be easily destroyed by the impending freeze, possibly damaging or killing the entire plant. Once the freeze is upon us, and the plant is completely dormant, you can go ahead and cut back the shrubs that will bloom on new wood if you want to. Most people simply prefer to wait for early spring when the weather is nicer to work outside. Shrubs that bloom on old wood should always be pruned just after they bloom.

Besides concerns for wildlife, blooms, and plant health, there is one other consideration. It involves a favorite gardener's term called "winter interest". We want our gardens to look good through all four seasons. In the winter, we lose the beauty of the flowers, but evergreens, grasses, shrub skeletons, garden ornaments and standing perennial seed pods can all help to provide winter interest. When the snows arrive and clothe the garden in a coat of white, winter artistry is at its best. The accompanying photo shows a little of my idea of winter interest.

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