Beaver damage to trees is a serious concern for property owners near waterways, as these rodents primarily feed on the inner bark layer, a process known as girdling. Girdling occurs when a beaver removes the bark entirely around the circumference of the trunk, cutting through the vascular tissues. This action severs the phloem, which transports sugars produced in the leaves down to the roots, eventually starving the tree’s root system. The ability to save an affected tree depends entirely on the depth and extent of this damage.
Assessing the Extent of the Damage
The first step in any repair attempt is a realistic diagnosis of the injury to determine if the tree is salvageable. The most damaging part of the injury is the removal of the cambium layer, a thin, active layer of cells situated between the bark and the wood. If the cambium is completely removed around the entire trunk, the tree is considered fully girdled and terminal, as the vascular connection cannot be re-established.
Trees that are only partially girdled, meaning less than half of the circumference has been affected, have a much higher chance of survival. If more than 50% of the trunk’s circumference is damaged, the prognosis is often poor, and repair efforts may be impractical. Inspect the wound carefully to confirm the depth of the damage, noting whether the beaver removed all layers down to the hard, inner wood (xylem).
Immediate Repair Procedures
If the tree is only partially girdled, the immediate goal is to clean the wound and encourage the tree to seal the injury naturally. Start by performing bark tracing, using a sharp, sterilized knife to cut away any loose, torn, or ragged bark edges from the wound. This shaping creates a clean, smooth margin that allows the tree’s wound-healing process, known as callusing, to begin efficiently.
For wounds that cover a significant portion of the circumference, the most advanced repair method is bridge grafting, which physically restores the severed vascular connection. This technique requires using dormant scion wood, which are pencil-thick shoots of the previous season’s growth, collected while the tree is still dormant. The grafting is performed in early spring when the tree’s bark is “slipping,” meaning it separates easily from the wood.
The scions are cut into wedges at both ends and inserted beneath the bark above and below the girdled area, effectively bridging the gap. Scions should be placed with a slight upward bow and secured with small tacking nails to ensure firm contact between the cambium of the scion and the tree trunk.
The entire repaired area, including the ends of the scions, must then be covered with grafting wax or a water-based asphalt emulsion to prevent the tissues from drying out. Although arborists often discourage the use of traditional wound dressings, a protective coating is necessary in this context to keep the delicate scion wood moist and viable.
Long-Term Care for Injured Trees
After the immediate repair, the focus shifts to reducing environmental stress to allow the tree to dedicate its energy to healing. Adequate hydration is a primary concern, so the tree should receive deep watering, especially during dry periods, to support root function and canopy health. This is important because the roots are already stressed from the interrupted supply of sugars.
Continuously monitor the wound site for signs of infection, decay, or the formation of callus tissue, which appears as a swollen, rolled margin around the injury. Successful callus formation indicates the tree is actively closing the wound and integrating the bridge grafts. Avoid applying heavy, high-nitrogen fertilizers, as the tree needs to prioritize wound closure over rapid new shoot or leaf growth.
Prevention Strategies
The most effective way to prevent future damage is by installing physical barriers around the trunk of the tree. Use heavy-gauge wire mesh, specifically 14-gauge welded wire (about two by four inches mesh size), to create a protective cylinder around the trunk. Lighter materials, such as chicken wire, are not robust enough and can be easily chewed through or pushed aside by beavers.
The wire barrier should be a minimum of three to four feet high to account for snowpack. Leave a gap of six to twelve inches between the wire mesh and the trunk to allow for future tree growth and prevent beavers from chewing through the wire onto the bark. An alternative method involves coating the tree trunk with an abrasive mixture of exterior latex or oil-based paint mixed with fine-grained sand. This gritty coating makes the bark unappealing to beavers without harming the tree.