Hungry animals make their mark during winter

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The trunks of this spring witchhazel show the scars of two years' of rabbit damage. Arrows point out a year-old wound (blue arrow) and new damage (orange arrow). 

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Girdling is a killer

When rabbits and voles (meadow mice) gnaw on tree trunks and shrub canes during winter, those parts of the plant may die right away -- simply not leaf out.

If the damage is extensive without completely circling a stem, the leaves may grow only to wilt suddenly and die a few weeks later or during the first hot spell of summer. That's because the critters' gnawing stripped away the cambium, breaking the path starch (energy) must take to flow from leaf to root. Sans cambium the foliage can grow, because it uses water coming up through the woody xylem of the canes. However, those leaves cannot repay the favor by nourishing the roots. So the roots starve, then foliage and wood die, too.

Strategy for controlling animal damage

This viburnum (below, left) has been stripped of cambium. We'll cut the canes back (for the second year in a row) to see if the plant has the energy for yet another comeback. (To see rabbit chewed burning bush cut back, see Remedy rabbit damage.)

Our strategy in this garden has been capitulation plus removal of target plants and replanting with non-food species. All other options -- animal trapping, fencing and the use of repellents -- have been vetoed by the owners. Per that strategy, since this viburnum can't provide us with flowers when it's cut back annually, we'll dig it out and plant an unpalatable substitute, such as elderberry (Sambucus nigra).

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Nearby (above right), rabbits nipped off all this weigela's canes, except one. We could leave that branch to bloom but it would only look silly. We'll cut it back to the ground to match the others, and accept just one late-season bloom from this plant. Too bad, since without rabbits we normally manage weigela to bloom twice per year.

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Low-down voles

Voles -- also called meadow mice -- tend to do their damage at the very base of a trunk, or even just below the soil line where roots meet trunk. They're as effective as rabbits at girdling a plant but because the damage they do can be more easily overlooked, the plant's death may seem more mysterious. (Control measures for voles in Growing Concerns 462.)

Right: Only when we cleared mulch and soil away from the tree's trunk could we see the bark had been gnawed by voles.
Far right: Rabbit chewing is usually much easier to see.

Specialized grafting called bridge grafting can reconnect the cambium above and below girdling damage. For a very special tree it may be worth looking into, but don't expect to hire it done. (See Growing Concerns 566.)

Deer sign

Deer tend to browse higher than rabbits although both critters may favor the same plants.

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Above, left: The base of this hedge is bare from deer browse.

Above, right: Gardeners should learn to recognize animal damage in early stages, and exclude or repel the culprits. Do you see where browsing has begun on this arborvitae?

Below: Yes, there's the deer sign.

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Below, left: Deer have an overbite so the stems they feed on tend to have one ragged edge. Below, right: By comparison, rabbits make very clean cuts.

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Other signs distinguish between garden-raiding critters, such as deer's triangular hoof prints and deer droppings. (a.k.a. manure, dung, poop.)

These arbs (right, arborvitae or eastern cedars, Thuja occidentalis) have not discolored from winter cold, by the way. It's normal for this variety for the most exposed foliage to become bronze as its internal chemistry changes to protect cell fluids from freezing. It will become green again as the weather warms and days lengthen.



Focus, not flowers!

We sometimes miss animal damage because we're starved for color and distracted by flowers in spring. For instance, we almost missed the new chewing on this spring witchhazel (Hamamelis x mollis 'Arnold Promise').

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We watch for patterns in animal damage, to help prevent recurrence. These two spicebushes (below, Lindera benzoin, a yellow flowered, spring blooming native) were the same size last year. Look carefully. (We know; it is hard to see bare canes against mulch in spring!) See how much more of the far spicebush has been eaten?

Notice, too, that it's the spicebush closest to the junipers that's been most heavily browsed. Rabbits are skittish creatures that stick close to cover. A fence with very small openings along the edge of the junipers may do as much to protect the spicebushes as caging around each bush. Use rabbit hutch wire, or hardware cloth; rabbits can squeeze through chicken wire opening.

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So look down for scrapes, rabbit- or deer dung, and hoof prints as you assess the winter's toll. We know a specimen such as this weeping white pine (at right, Pinus strobus 'Pendula') may be your special love and so you worry about its unusually pale foliage. Still, try to look over everything. If you lose those shrubs in the background (below), it may ruin your view of the pine.


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