Snow melt reveals lawns that have been covered up for many months, at the same time exposing damage to lawns and plants. This column visits about the most common lawn issues exposed this spring. 

Rabbits, Squirrels & Voles Oh No!

This spring, one of the most common questions I have been getting is, "what caused all the rows of dead grass in my lawn?" Voles are likely the culprit. They are quite similar to field mice that are found in fields but also are common in home lawns and yards.
Unlike lots of mammals, voles remain active all winter long, happy to scamper around in their under-snow tunnels, feeding on grass, other plants and seeds. They will often eat the grass right down to the ground and leave the leftover dry grass behind or pile it up in little nests during the winter. They often leave these long, twisty narrow trails over the lawn. If you see these, just rake up the dead grass and get rid of it. Usually this damage is just cosmetic and chances are that the lawn will grow back just fine later this spring.
Voles will also feed on woody plants, often down close to the ground, near the base of the plant where it was likely covered with snow and provided a protected place for these little critters to live during the winter. Check the base of your shrubs and trees to see if there is damage.

Voles are small field mice with tiny mouths so they damage the stems of plants mostly by gnawing away at the bark, taking lots of small bites. In many cases they will feed all the way around a stem which will usually kill the stem and in some cases the whole plant.
Rabbits and squirrels will also feed on trees and shrubs, usually eating the bark or in some cases cutting off the whole plant. Rabbits will take out much larger chunks of bark with each bite or leave an angled cut to the end of the stem. Squirrels will usually feed higher up in the tree. Often times, you will see individual branches in a shrub, like a juniper or yew that turns brown. If you check it out you will likely see that the bark was chewed off near the base. All you can do is cut off the dead branch close to its source.
Winter burn

Winter burn on trees and shrubs is the other most common type of damage that gardeners might see in their home yards this spring. Winter injury occurs most often when we have windy conditions. It will be worse during sunny weather or with windy and extremely cold weather because the air is so dry that it pulls moisture out of the plant's needles. The injury occurs because the plant is in frozen or dry soil so its roots cannot take up the water needed to replace what is lost so the needles become desiccated and turn brown.
In some cases, winter desiccation injury of evergreens can be cosmetic with the browned needles being hidden by new green needles when growth resumes in the spring. The needles that turned brown will not green up again but will probably fall off during the spring and summer. In more severe cases, the small buds on the twigs are also desiccated and killed, in addition to the needles so that the plant will not green out again.
Surrounding branches may eventually cover the browned portion of the plant but winter injury like this will often recur in future years. Thorough watering in late summer and fall can help but in many cases the real problem is that the site is not appropriate for the plant that was selected.
Extreme cold temperatures can also cause winter injury, to both evergreen and deciduous trees and shrubs. But that type of injury will most likely affect the buds on the twigs of the trees or shrubs.
Injury like this can occur at any time of the winter but will often happen in the spring, as plants begin to come out of dormancy and are not as cold hardy as they were earlier in the winter. If you planted a tree or shrub that is not completely hardy to your hardiness zone, you may be more likely to suffer partial damage or the complete loss of a tree during a tough winter.
The flower buds of certain types of trees are especially sensitive to cold in the spring. Apricots, for example, will usually survive our winters but they tend to come out of dormancy earlier than many of our other trees and shrubs. Their flower buds are generally the first buds to break and they are particularly sensitive to late spring frosts and cold spells. Consequently, while many people grow apricots, they may only get a fruit crop every three to four years, if they are lucky. In some cases the root system may be killed by severe winter conditions. If that happens, the tree may leaf out but then the leaves suddenly turn brown and the plant is dead.
Benefits of mulching

Most of our herbaceous perennial plants are more protected from winter injury because generally the plant's buds are located beneath the ground which offers them some protection from the cold. Good snow cover during the winter offers significantly more protection from the cold.
Unfortunately, snow cover often comes and goes, depending on the temperature. Mulching your plants, particularly those that might not be fully hardy in your area, can offer winter-long protection from the coldest temperatures during the winter.
Speaking of mulch – don't be in too much of a hurry to take that mulch off the plants this spring. It will still offer protection to the plants, especially as we start getting some warmer days and those buds under the soil start to grow.
Utilizing plants that are hardy to your area is usually the best way to avoid winter injury but many of us like to push the plant envelope and try some of those Zone 5 and even Zone 6 plants once in a while. I have to admit, that it is fun to gamble a little bit in the garden and try some of those more "exotic" plants and see what happens. Some years you might get lucky and in other years, not so much. But at least you had the fun of growing something that most of your other gardening friends did not have in their gardens.

Column by David Graper, SDSU Extension Horticulture Specialist and Director of McCrory Gardens


Most perennials have buds that are at or just below the soil surface so they are usually protected from winter injury.


Vole damage to a Viburnum shrub.


Extensive vole damage like this will likely kill the shrub.


Some evergreens like this dwarf Alberta spruce are particularly prone to winter burn.


If the buds in the tips of the twigs are OK they can grow out to cover some of the browned needles.