Beaver Proofing Your Garden

Keeping beavers away can be quite a challenge. Ill.: uihere.com, netclipart.com & www.kindpng.com, montage: laidbackgardener.blog

Few animals cause damage to gardens quite as quickly as beavers. Yes, Japanese beetles and deer can provoke considerable destruction, but they don’t take out entire trees the way beavers do. One day, you have a nice shady nook; twenty-four hours later, it’s in full sun without a tree in sight. What a shock! 

Since beavers are often associated with cottage country, you might well come to reopen your summer home in the spring only to find beavers have turned a forest into a field. Doubly so, as they do most of their damage in late fall, when the cottage is boarded up for the winter and you’re not around to ward them off.

Beavers: Wider Ranging Than You’d Think

You might think beaver proofing would only be a subject of interest in Canada, as the beaver is its national animal and it’s particularly abundant there, but no.

Beavers, once nearly driven to extinction in the southern 48 states of the United States by overhunting, are recovering and reoccupying their former range, even showing up in large cities, like Chicago and New York City. And the North American beaver (Castor canadensis) has been introduced and is spreading in Chile and Finland.

Also, the Eurasian beaver (Castor fiber), likewise once nearly pushed to extinction, is also returning to or being reintroduced to its former haunts, that is, most of temperate Europe and Asia. Even Great Britain, where the Eurasian beaver went extinct in 1526, now has a few colonies over 450 years after their disappearance, thanks to reintroduction programs.

Rodents With Big Teeth

Beavers are rodents, renowned for their large, flat, paddlelike tail. They’re the world’s second-largest rodent (only capybaras are bigger), weighing up to 60 lb (27 kilograms) and have huge teeth that grow all their life. They have to gnaw on wood to keep their incisors in check. They can cut down a small tree in minutes and even a large one in barely an hour. And few animals are better at digesting wood than beavers. 

Semiaquatic, beavers depend on water, frequenting ponds, lakes, rivers, streams, marshes and swamps. Where water is not available, they create it, damming streams to make ponds and digging canals. On land, they’re awkward and very vulnerable to predators. That’s why, when feeding, they rarely range more than 100 feet (30 m) from a source of water they can escape into. 

Beavers are best known for feeding on trees, gnawing on their trunk and toppling them, often so they fall into the nearest body of water. From there, they can then feed on the buds, stems and twigs undisturbed. If not, they’ll cut off the branches and carry them away. They also strip off and eat bark from trunks that land in or near the water. Woody plants are largely winter fare, though. They often go into a frenzy of tree harvesting in late fall to stockpile a cache of branches they store underwater and can then leisurely gnaw on over the winter. (Beavers don’t hibernate.)

In summer, beavers feed mostly on softer foods, especially aquatic and marginal plants—they’re especially fond of cattail rhizomes and waterlily tubers—, but also grasses, ferns and other herbaceous plants, fallen fruits, mushrooms and more. Contrary to popular belief, they don’t eat fish.

Keeping Beavers at Bay

Rule number 1, of course, is to settle far from water. That waterfront lot will look much less charming with all the trees chopped back. True enough, beavers do dam creeks and thus flood formerly dry land, but if any development is under threat of flooding, you can be sure that the authorities will become involved. (How beavers causing flooding are treated—trapping, shooting, beaver baffles on dams, etc.—will largely depend on local legislation.)

Rule 2 is … don’t encourage them by planting susceptible species. Beavers have distinct preferences when it comes to trees. Poplar and aspen are by far their favorites and they’re the trees they’ll travel farthest from water to harvest, but also willow, alder and some birches. They also attack maple, oak, apple, cherry, beech, ash, hornbeam and other deciduous trees, but usually only if they are easily accessible. Note too that they’ll harvest specimens of any size, from saplings to fully grown trees, of favored species, but only small ones of less desirable ones. Unless starving, they usually avoid conifers like pines, spruces, firs, arborvitae and hemlocks as well as red maple (Acer rubrum). 

Eventually, beavers will exhaust the supply of food species locally, then the colony will move on, but that can take many years. Once they’ve left, though, you can relax for a while. Normally, it will be at least 10 to 15 years before there is enough regrowth of woody plants for beavers to return to a given area.

Protecting Your Trees

If you have any reason to suspect there are beavers in your area, you’ll have to either let them do their harvesting and live with the results … or react by protecting your trees in various ways.

The most effective method is to wrap the trunks of your most important trees in a cylinder of heavy gage wire fencing. The fencing should be at least 4 feet (1.2 m) high, but in areas with major snow cover, it needs to be at least 2 feet (60 cm) higher than the deepest snow. You may need to cut and splay out the bottom of the cylinder to protect prominent roots from gnawing or to fit a sloping ground. You’ll be able to leave the fencing in place for years as long as you allow some room for trunk expansion. Note that the shiny gleam of galvanized metal quickly fades to a fairly innocuous dull gray over time. Well done, this method is 100% effective.

You can also protect a yard or grove of trees by surrounding the area with fencing. This needs more carefully installation, especially on uneven terrain: beavers quickly give up on trunks covered in fencing, yet will try to dig under an independent fence if they see the slightest space underneath, so it must be placed very carefully so it touches the ground along its entire length, leaving no gaps at all. And again, it has to be at least 4 feet (120 cm) tall and 2 feet (60 cm) higher the potential snow cover.

An electric fence placed about 4” (10 cm) above the ground is a more aesthetic way of surrounding a grove of trees, even an entire yard. You can find this kind of fencing in farm supply stores, run by a car battery or solar power. Do check regularly that a fallen branch hasn’t shorted it out.

Other methods include painting bark with mineral or vegetable oil soaked in cayenne pepper or spraying bark with a scent aversion repellent such as coyote urine. The danger is that these are not always effective to start with, plus wear off at various speeds depending on local conditions. Certainly, they can’t be fully trusted in a rainy climate.

You may have better luck mixing sand into latex paint (bark-colored, one would hope!) and painting on the bark of the trees you want to protect. About 5 oz of sand per quart of paint (140 g par litre) is about right (more than that and the paint won’t stick properly). It works best on mature trees and lasts for years, but seems ineffective on saplings.

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Hopefully, one of these suggestions will be the right one when it comes to beaver proofing your property.