Deer most often damage plants by browsing new leaf tissue, buds, and small twigs. This is where a substantial portion of stored energy in the form of sugars and starches is located. Male deer also damage trees and shrubs by territorially rubbing their antlers on bark tissue, sometimes girdling and killing the plant.
Under heavy pressures, deer can eat entire shrub beds down to stubs in a few days browsing. A Whitetail Deer needs 6-8 lbs of food daily. One should consider what 6-8 lbs of buds and twigs from your plants would look like. Secondly, consider what 3 to 4 deer could eat overnight. Deer resistant shrubs should be the first option in a multi-tiered control strategy.
While rabbits obviously do not eat the same quantity as deer, the way they feed is much more damaging to a plant's long term health and growth. Rabbits will browse both bud and twig tissue, as well as eat bark tissue from select plants. This removal of bark severely restricts food and fluid movement throughout plant. Often the branch or entire plant may be girdled and killed. Sometimes damage goes unnoticed, as most damage occurs on lower branches and trunk, obscured by snow or vegetation.
Mice and Other Rodents
Like rabbits, most damage occurs on the bark tissue of the plant's interior. Mice and other rodents also feed on root tissue where available. Often times, dense plants cannot be treated with repellants effectively. In these situations, population control with traps or baits is the most effective solution.
Effective management often begins before installation. Deer resistant plant species should be selected whenever possible to minimize future problems and associated costs. The location of more desirable plant material should also be scrutinized. Please see Rave's Selection of Deer Resistant Plants.
Sites with exceptionally heavy pressures or a history of severe recurrent damage should be considered for fencing. An 8ft nylon fence on metal stakes or poles is installed in late fall around damage prone plants or beds. Fencing is monitored through winter and removed in spring as native food sources resume. Fencing can also be applied around the trunks of valuable trees in late summer to prevent buck rub damage.
For most purposes, repellants are classed into two groups: seasonal and dormant.
Seasonal Repellants - These are applied throughout the growing season and conditions the deer that plants are unpalatable in odor and taste. These repellants are generally organic and do not harm the animals if ingested. These repellants do not typically last as long as dormant repellants and must be reapplied as growth occurs.
Dormant Season Repellants - These are generally chemically based and very long lasting when mixed and applied correctly. These repellants can impact photosynthesis and transpiration and should be applied when growth stops for the season. Typically late fall and mid winter are optimum treatment times for pressured areas.
Please be aware that repellants will reduce damage, usually quite significantly. However, they should not be considered deer-proofing. When animals are faced with bad taste or starvation...survival wins. Both repellants discussed are also effective against rabbits and rodents.