Ask Dr. Phipps: Fall Care

By Phipps Master Gardener

Have a question about your perennials, houseplants or turf grass? Worried about pests in the garden, hydrangeas that won't bloom, or tomatoes that died on the vine? Dr. Phipps can help! Ask Dr. Phipps is a free service provided by Phipps Master Gardeners. Contact us with your questions and you may be featured in an upcoming blog post!

Q: Do you recommend cutting all perennials down before winter? 

A: It depends on what perennials you are growing. Some perennials should be cut back now and others should be left until spring, while others, like big leaf hydrangeas, should never be cut back unless there is damage or a problem.

Without knowing all the plants in your garden, it is hard to give specific advice. You can find correct care of each individual perennial if you google "Care of __________" for each of the plants you have.  You may want to get a gardening reference book, such as The Well-Tended Perennial Garden by Tracy DiSabato-Aust. There is great information in this book with regard to perennials and the back has a long section that lists perennials that require maintenance in the spring and perennials that require maintenance in the autumn (pgs. 364-366).

Some rules of thumb —

• If the plant has a lot of seeds or dried flower heads that will provide food or cover for birds or wildlife through the winter, leave it alone. In the next few weeks as we develop frost, a lot of perennials naturally die back to the ground and you can remove dead material from the ground.  
• If a perennial provides winter interest, such as the colorful stems of a red twig dogwood or the fun texture and shapes of many perennial grasses, you should leave it unpruned.
• If you absolutely must trim a perennial bush or tree it is better to wait until we have a deep frost and it goes dormant. That way there is less chance of winter burn or disease. Cutting back bushes or trees right now doesn't give them enough time to harden off before the frosts arrive and then there can be some freeze damage that will really harm them.
• Never trim your spring blooming bushes in the fall. You might be cutting off next spring’s flowers, as is the case for azaleas and rhododendron. Butterfly bushes should be left until the spring and then trimmed down to about 6-9".  If you have "Knock-out" roses, you should trim them in the spring, as well.

You may want to start keeping a record of the plants that you have and what you do to care for them and when. It is helpful as the years go on.