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Covering Perennials for Winter

Gardeners are frequently disappointed when certain perennial flowers die over winter. Plants such as chrysanthemums and iris will survive severe North Dakota winters if you protect them properly.

Be sure to select winter hardy perennials. Avoid planting perennials in poorly drained locations where they are subject to root rot.

You can give most perennials good winter protection by placing a four to six inch layer of loose mulch material like straw, compost, or leaves over the plants late in fall after there is some frost in the ground. This mulch protects the "crowns" or growing points of the plants, and helps keep the soil frozen all winter.

Without mulch, the soil may thaw during warm winter weather. When it refreezes, the soil heaves. This alternate thawing and freezing damages many perennials, especially very shallow-rooted perennials.

Some perennials, like chrysanthemums, can use even more protection. After mum flowers and most of the leaves have browned from frost, mound soil to about eight inches around the base of the plants. Cut branches back to 10 inches above the soil line. Then, once the soil mound begins to freeze, cover it with a loose four to six inch layer of straw or compost.

If you have further questions, please contact your local county extension office for further information.

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For More Information Contact your North Dakota County Extension Office of the NDSU Extension Service for additional information or see our main NDSU Web Page for publications and articles on Agriculture, Horticulture, Youth and Family, Business and Community and Food and Nutrition at  http://www.ag.ndsu.nodak.edu/