Garden Topics: Winter Desiccation Injury of Evergreen Shrubs and Trees
Have you noticed dead leaves, browning, discoloration and leaf spots on your broad-leafed evergreens once spring has arrived? Winter burn or plant death occurs when winter winds draw moisture out the leaves of evergreen plants while the soil is frozen. Plant roots are unable to uptake water when the soil is frozen, and so leaf damage results.
Broad leaf evergreens such as Rhododendron are more susceptible to winter desiccation than needle type evergreens due to larger leaf surface area, but conifers may also be affected. Some plants will exhibit overall yellowing and browning or may only show the burn at margins or tips. If the burning is extensive, the tree or shrub generally drops the affected leaves: plant death results in severe cases.
Evergreens planted late in the season are at greatest risk because their root system had little time to expand. It is critically important to take special care to protect these plants
- Proper watering can is a critical factor in
winterizing evergreens. If autumn rains have been
insufficient, give plants a deep soaking that will
supply water to the entire root system before the
ground freezes. Watering when there are warm days
during January, February, and March is also
- A 3-inch layer of mulch will reduce water loss
and help maintain uniform soil moisture around
- Anti-desiccant sprays can be applied in late
fall and mid-winter if desired and may provide some
protection. One of these products are sold under the
trade name Wilt-Pruf.
- Small evergreens can be protected by using windbreaks made out of burlap, canvas, or similar materials. Windbreaks will help reduce the force of the wind and shade the plants and thus reduce moisture loss. They can be created by attaching materials to a frame around a plant. Black plastic should be avoided as a material for wrapping plants.