Drought conditions in the fall can damage evergreens in the winter
Protecting evergreens from dry conditions now can mean healthier plants come spring.
Fall in Michigan is always spectacular as trees and shrubs put on a show of colors. While we enjoy the display of red and orange leaves on sugar maples, yellow needles on pines and other conifers is disconcerting to homeowners. The yellowing of older needles and their eventual drop is a natural process that can be seen each autumn. Though we call pines, spruces and other conifers evergreens, they do not retain all their needles from past years. Different species of pines vary in the number of years needles are retained on the tree. White pine may retain a couple years of needles while a Norway spruce can retain over five years of needles. Retention can also vary in the landscape due to insect and mite feeding, fungal damage and environmental stress.
The drought this past summer left many plants, including evergreens, stressed and weakened. The National Drought Mitigation Center listed conditions in Michigan as “abnormally dry” to “severe drought” on July 17, 2012. A couple counties on the border with Indiana were in “extreme drought” conditions. With cooler, fall weather and some rainfall, we are now listed as “abnormally dry” across most of Michigan’s Lower Peninsula.
The drought of 2012 may be history for us, but landscape plants will take a few years to fully recover. Evergreens may need special care yet this fall. Don’t be too quick to put away the hose and call it a season. Though conditions have improved, it is still drier than normal. Continued dry weather is problematic especially for evergreens at a time when water is so critical for their health prior to winter. During the winter, exposed needles and leaves of evergreens such as spruce, pine, boxwoods and rhododendrons are at the mercy of nature as cold winds pull moisture from the leaves. Once the ground freezes, the plant cannot bring any more water in through the roots. If water is lacking within the plant due to an abnormally dry autumn, then needles and leaves may die as water is lost during harsh, winter conditions.
Steps you take this fall can prevent needless damage to evergreens in your landscape. Watch weather patterns and water evergreens when nature does not supply an inch of water per week. If you are unsure of whether a plant needs to be watered, take a shovel or trowel and dig down a few inches to check moisture in the soil. Watering the root zone of the plant with a slow trickle will help wet the roots while not causing water to runoff or leach. Allow soils to dry partially before providing any more water. Be water wise, know the moisture needs of plants in your landscape and provide needed water when conditions call for it.
See the following links for more information on drought conditions and winter injury to plants.
- U.S. Drought Monitor
- Winter Desiccation Injury of Evergreen Shrubs and Trees
- MSU Extension’s Drought Resources