By Kathleen Cue, Nebraska Extension Horticulture Educator in Dodge County
Once gardeners and gardens have survived the heat of summer, cooler weather offers an opportunity to complete some simple tasks to ensure perennial plants emerge in good health next spring.
If the foliage of perennials has been disease-free, wait to cut them back until spring. This benefits our native bees because 1/3 of native bees overwinter in cavities, which includes the hollow stems of plants. By waiting to cut back perennials until spring, these pollinators are given a fighting chance to survive. In addition, many perennials are beautiful in the winter landscape, showing off the petal-less cones of purple coneflower and the gracefully waving seed heads of prairie dropseed. Stems left in place serve as reminders where the slow-to-emerge balloon flowers and hibiscus will be in spring. Stems catch leaves and other bits of plant debris, making them self-mulching.
Deadheading and Clean-Up
Perennials that are aggressive self-seeders should be deadheaded in the fall to cut down on the number of volunteer seedlings in the spring. Perennials like garlic chives have charming flowers but the number of seedlings one plant produces is alarming. On the other hand, coneflowers provide seeds to overwintering songbirds and should be left in place. Daylilies present a ragged appearance after blooming, so gently tug out dead leaves and spent flower stalks. The brown tips of the long leaves can be trimmed away. Fungal spores of powdery mildew and botrytis overwinter on standing stems of peonies, so clean up to reduce inoculum for next years' plants is helpful.
Perennials need an inch of water per week. This year's drought conditions have not abated, even in locations where rainfall was 4 inches or more. Before ground freeze, water plants so the entire area receives an inch of moisture. Use straight sided cans, like tuna fish or cat food cans, when irrigating to provide guidance when this one inch of water is achieved.
One of the many benefits of mulch is to serve as a barrier from quick air temperature fluctuations. Most perennials nicely withstand deep drops in temperature--as long as changes occur gradually. In the Midwest, this can be a challenge even for the toughest perennials. Mulches trap protective air pockets around roots, buffering the effects of quick temperature changes. Wood chips, shredded bark, straw, pine straw and grass clippings are good mulching materials. Rock is not a good mulching material because it readily transfers the air temperature to roots, making roots susceptible to cold injury when temperature change is swift. Layers of wood chips should be no deeper than 3 inches and placed about 2 inches away from plant crowns to ensure good air circulation. Add mulch to maintain this 3-inch depth as it decomposes.
Watch for a continuation of Fall Care of Perennials, when the topics of Fertilization, Digging and Dividing, and Fall Planting are covered.
Go to Dodge County Horticulture Web Page for more gardening information.
Photo: Perennial Garden