March 1, 1996

How Woody Plants Survive Extreme Cold


The ability of a tree or shrub to survive an Iowa winter depends on the seasonal change in its metabolism to a quiescent or dormant state known as acclimation. The first stages of acclimation are induced in early autumn by exposure to short days and nonfreezing chilling temperatures, both of which combine to stop growth. But to survive the kind of low midwinter temperatures recently experienced in Iowa, woody plants must be exposed to temperatures at or below freezing for some time before they become fully acclimated.

Potential Damage from the Record Low Temperatures in February


In early February 1996, record low temperatures were set in many portions of Iowa. Temperatures of -30 F or below were common, particularly in the northeast where -46 F was reported at Decorah. Although the bitter cold came at a time when most fruit crops should have been at or near their maximum hardiness, such low temperatures approached or dropped below the maximum hardiness of many perennial plant species grown in our climate.

Native Woodland Wildflowers for the Home Garden


When selecting plants for the shade garden, one group of plants that is often overlooked are native woodland wildflowers. Since they are native to the state, woodland wildflowers are completely hardy. They also perform well when given a good site. Many are very attractive. When browsing through garden catalogs this winter, consider some of the following woodland wildflowers.

Native Woodland Wildflowers for the Home Garden


When selecting plants for the shade garden, one group of plants that is often overlooked are native woodland wildflowers. Since they are native to the state, woodland wildflowers are completely hardy. They also perform well when given a good site. Many are very attractive. When browsing through garden catalogs this winter, consider some of the following woodland wildflowers.