All evergreens, and particularly broad leaf evergreens such as boxwood and rhododendron, are susceptible to winter desiccation. Winter desiccation also is referred to as winter burn or winter browning. Desiccation occurs when the evergreen's foliage loses moisture due to the bright winter sun and harsh winter winds. In winter the plants are not able to absorb enough additional moisture from the soil to replace the water that evaporates from the foliage and stems. In addition to making sure the plants are well watered before the onset of winter there are a few other measures homeowners can take to protect the plants.
Boxwood (Buxus sempervirens) is a dark green evergreen native to southern Europe and northern Africa. It usually grows to a height of three to four feet in the Iowa climate, and is popular for borders and hedges because of its dense, dark green foliage. Boxwood requires fertile, well-drained soils and prefers wind protection if grown on an exposed site.
Typical signs of freezing injury are a blackened/brownish discoloration or bleaching of plant tissue. If the freezing injury kills a significant number of buds or cambial tissue, the plant may die or suffer so much crown die-back that it becomes unusable. If freezing injury is limited to flower buds and shoot dieback, it may require corrective pruning and time to allow the plant to grow out of the damage.
Spruces are a favorite evergreen for yards and windbreaks in Iowa. However, they are susceptible to a few problems that can leave them unsightly. Knowing about these common spruce ailments is the first step toward minimizing problems with these beautiful trees.
Needles, bark and cones are among the characteristics that can help you determine the type of tree in your landscape.