Winter burn is a common occurrence to boxwood, holly, rhododendron, azaleas and some conifers. Many plants will get some leaf spotting due to moisture loss. As moisture leaves the plant, the roots need to replenish it. During our often extreme winter weather plants are dormant, but as the weather start it’s up and down cycle in early spring, those plants/leaves begin to transpire (the evaporation of water from the plant). If the ground is still frozen, the roots can’t take up any water, thus damage to leaves or needles, dehydration or even death may occur.
Winter burn causes the scorching of leaf tips, browning of needles from the tip down, or death of the terminal buds. Symptoms often develop and show up when temperatures warm up in spring or early summer in our region. This type of winter damage is often misdiagnosed as an infectious disease or damage from excessively cold temperature.
Prevention. Carefully choose plant material, avoid less hardy trees and shrubs that are known to suffer from winter burn. Design natural windbreak landscapes, layering your planting area with very hardy trees and shrubs.
Avoid planting broadleaved evergreens like rhododendron or pieris in areas of high wind exposure.
In the fall, deeply water plants before the ground freezes, and during the winter months when temperatures are above freezing but there is little precipitation. This is especially important for young or newly planted evergreens.
Wrap problem plants with burlap or other material to protect from wind and subsequent moisture loss to evergreen shrubs and small trees. This works well for Boxwoods or smaller evergreens.
Do not plant evergreens right next to roadways that get treated for snow and ice with damaging salt mixture.
Try spraying with an antidisiccant. This protective oil based spray forms a coating on the plants, reducing excessive moisture loss. It’s also often used on Christmas cut greenery. It’s best to use in the fall before temperatures drop below 50 degrees. Do not use this type of product on any “glaucous” conifer…ie: Blue Spruce. It can damage the blue needles.
The pine in the picture is showing winter burn damage. This is most likely a combination of three factors: 1) this is south-facing, so heat from solar radiation will cause the needs on that side of the tree to lose water more rapidly, 2) salt spray from the road during winter can burn the foliage, and 3) increased wind (relative to the north side) can lead to needles drying out.