While the weather is still mild enough to work outside, think about the hard times ahead — for animals.

In winter, when the supply of fresh grass and leaves is gone, animals turn to bark, twigs and buds. “Your garden becomes a food pantry,” said Julie Janoski, manager of the Plant Clinic at The Morton Arboretum in Lisle.

The damaging diners include deer, squirrels, chipmunks and voles — mouse-sized animals that can tunnel through snow and mulch. Rabbits standing on their hind legs can reach at least 3 feet high into trees and shrubs.

It’s not possible to protect the entire garden, but you can fortify the most vulnerable plants, such as new trees and shrubs. They have tender bark that is easy to chew and digest. Here are some tips for guarding them.

Guard young bark. For a young tree, make a cylinder of sturdy 4-foot-high wire fencing. It should be wide enough to keep animals several inches away from the trunk.

Encircle the trunk and bring the edges of the fencing together. Overlap the edges an inch or two and use wire to secure them. Anchor the fencing firmly by wiring it to a couple of stakes in the ground and pin the lower edge to the ground with long landscape staples.

The best way to protect a young tree or shrub against animals in winter is by surrounding it with sturdy wire fencing. (Beth Botts/Morton Arboretum)

“You don’t want a hungry animal to be able to pry the fencing open, wrench it loose or push it over to get close to the bark,” Janoski said.

To hold off tiny mice and voles that could slip through the fence, install a temporary plastic tree guard — basically a plastic cylinder a few inches high — around the base of the tree.

Tree wrap tape is not a good idea, she said. “It traps moisture against the bark, which can lead to decay,” she said. “It causes more problems than it solves.”

A newer kind of tree guard, a spiral of plastic that you can wind around a trunk and lower branches, can deter animals to some degree, although it’s not as effective as wire fencing. Be sure the plastic has holes to allow air circulation and remove it in early spring.

Defend twigs and buds. Slender, soft young branches and twigs are good animal food. Young shrubs with succulent stems may be eaten right down to the ground.

Many shrubs in winter have leaf and flower buds that attract animals because they are relatively rich in protein. “Rabbits have been known to nibble all the buds right off a branch,” Janoski said.

Which plants should you try to defend? “If a shrub has been damaged in previous winters, it obviously needs protection,” she said. “Smaller, newer shrubs less than 3 feet high are also tempting targets.”

Protect them with a wire-fencing cylinder that is 4 feet high and wide enough to keep animals from reaching through the mesh to the branch tips.

Deer are tall enough to nibble the branch tips of a young tree. To block deer, fencing needs to be 8 feet high.

Large, established shrubs can generally survive. “If a big old lilac or ninebark loses a few buds or twigs from lower branches, it’s not a tragedy,” she said.

Mulch carefully. Every young tree or shrub should have a layer of mulch over the surrounding soil, to protect it from temperature swings, maintain soil moisture and enrich the environment for its roots. However, mulch that is too deep can create a danger: Small animals such as voles can burrow through it to feed on the bark.

To guard against burrowers, spread mulch just 3 to 4 inches deep in a wide, even layer around a tree or shrub. Then go back and make sure you have left an open space of several inches between the inner edge of the mulch and the trunk or stems. “Voles are prey animals, so they won’t venture into the open where they could be seen by predators,” Janoski said.

What about animal repellents? They vary in effectiveness, she said, and they may not work in the cold. “A physical barrier is a better bet,” she said.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.