Extension Spotlight

Dry weather damages even the most established perennials. The roots are what will be damaged. When do you water? And what perennials to cut back this fall and then next spring?

Deeply watering your perennials before the ground freezes goes a long way to helping them through the initial transition into fall. After that pay attention to winter precipitation and if it gets dry and warm over an extended period find a way to give your perennials some water. Water when the air and soil temperature are above 40 degrees Fahrenheit. A little bit of water in the winter goes a long way. Perennials on the west and south side of the house will need more water and will dry out faster even in the winter. Late fall planted or bare root perennials will need water through the winter when there is no snow cover.

Do you clean and cut back all perennials? Marginally hardy perennials such as chrysanthemum, hyssop and Montauk daisy should be cut in spring according to Penn State University Extension. It is also beneficial to provide some leaves for added winter mulch around the plants and to help collect moisture. Ornamental grasses are attractive and can wait until early spring to cut before the new growth starts. Evergreen and semi-evergreen plants can wait until spring. Some of these are hellebores and dianthus.

What about herbaceous perennials? Do they get their stems removed in the fall? These perennials dieback to the ground. Do cut back the herbaceous perennials such as bee balm, phlox, day lily, peony, columbine and Shasta daisy. Some herbaceous perennials have seed heads that benefit the birds. These are coneflower, black-eyed Susan, and oxeye sunflower that can wait until spring to cut back.

Mulching your perennial beds for winter helps mitigate the soil temperature and keep moisture from escaping. Placing pine boughs on more semi-evergreen perennials will help protect from the cold and exposure of the wind.