Structure: Build the Bones from Resistant Plants

Structure is what the garden looks like when nothing is flowering. Evergreens, hedges, walls, paths, the shapes that hold a space together in February.

February is also when deer browse pressure peaks. So the planting you depend on in winter is the planting most exposed in winter, and that collision is what makes structure a different problem here than in a garden without deer.

The mistake is one plant, and it is everywhere

Arborvitae is the default privacy hedge across most of the country. It is also rated Frequently Severely Damaged by Rutgers, the worst of four tiers. In the trees section, only four entries share that tier: plums, cherries, European mountain ash, and American arborvitae.

This is not a marginal call. The USDA Forest Service review of white-tailed deer foods ranks preference in decreasing order as young non-evergreen leaves, mature non-evergreen leaves, evergreen forbs, cedar leaves, deciduous woody browse, then conifer needles.

Cedar foliage, which is what arborvitae is, outranks deciduous twigs and every other conifer. It is the one conifer deer actively seek out rather than tolerate.

Western arborvitae, Thuja plicata, rates one tier better. That still leaves it in the half of the list Rutgers says should only be planted with fencing or repellents.

What actually decides the outcome is regrowth

This is the part that gets missed, and it matters more than the rating.

Arborvitae and most conifers carry no dormant buds along older stems. Foliage stripped below the browse line does not come back on that wood. Ever. Maryland Extension describes the result as a stemmed flute glass: a permanently bare lower section with a healthy top still growing above the reach of the deer.

Broadleaf evergreens are built differently. Boxwood, holly and euonymus carry dormant buds on old stems and can rejuvenate after damage.

Two plants can take identical damage in the same January and one is disfigured for its remaining life while the other is fine in two seasons. When you are choosing the bones of a garden, that asymmetry should weigh more heavily than the tier.

If something has already been hit, Illinois Extension advises waiting until mid-June before cutting anything out. Buds on arborvitae and juniper are hard to see, and a branch that has produced nothing by then is dead. Anything earlier is guessing.

The browse line, and why snow moves it

Damage runs from the ground to roughly six feet. Forest ecologists use the same figure as a diagnostic for overabundant deer: every palatable thing below about five or six feet is gone and the understory is hollow.

On a hedge, the practical version is that deer work the bottom four to five feet, taking tips as high as they can reach.

Snow raises the whole thing. Extension repellent guidance is written around this and it is easy to miss: treat to about six feet above maximum expected snow depth, not six feet above the ground. Two feet of settled snow is a two-foot ladder, and the part of the hedge that was safe last winter is not safe this one.

Conifer needles are a starvation signal, not a preference

Worth knowing because it explains why a spruce that has been fine for a decade suddenly gets hit.

Spruce, fir and pine needles made up 58 to 60 per cent of the rumen contents of starved deer autopsied in late winter during past population peaks. In healthy deer they are a small part of the winter diet.

So needle browsing on those species is a signal about the herd rather than about your planting. It means the population has outrun its food supply, and no plant choice fixes that.

Even cedar, the preferred one, is not sufficient. Deer fed unlimited straight cedar lost weight, and maintained weight better on a mixture of second-choice woody browse. Winter browse is poor food. They eat it because there is nothing else, which is precisely why a well-fed suburban hedge is attractive.

Once they start, they do not stop quickly

It takes up to four weeks of feeding on a new food source for a deer to build the rumen microorganisms needed to digest it.

That cuts both ways and mostly against you. A deer that switches onto your hedge in January has invested in being able to eat it, and it is not going to abandon that investment because you started spraying in February. It is a strong argument for having protection up before the pressure arrives rather than in response to it.

Product labels agree, if you read them closely. One directs application before freezing weather arrives, with a reapplication during a midwinter thaw. Another tells you to wait for above 35°F, because water freezing on treated foliage pulls moisture out and browns the leaf edges.

Structure that cannot be eaten

The most reliable winter structure is not planted.

Walls, fences, paths, steps, a hedge on the far side of a fence rather than in front of it, the shape of the beds themselves. None of it browses. In a garden under real pressure this is where the bones should live, with evergreens as the decoration on top rather than the thing holding the composition up.

Where you do want evergreen mass:

• Broadleaf over needled, for the regrowth reason above.
• Boxwood, American holly and Japanese pieris all sit in the top tier and all recover.
• Put anything needled where it is either fenced, close to the house, or genuinely expendable.
• If you want an arborvitae hedge, you are committing to protecting it every winter for its whole life. That is a legitimate choice, and it should be made deliberately rather than discovered in year three.

What Rutgers is and is not

The ratings above come from a list compiled with input from nursery professionals, extension staff and Master Gardeners in northern New Jersey. It is practitioner consensus rather than a controlled feeding trial, and the publication says so, along with the reminder that no plant is deer proof and that results depend on local populations and weather.

The browse chemistry work behind the arborvitae findings is worth one caveat too. Preference within Thuja plicata tracks monoterpene content, with heavily browsed trees averaging about half the monoterpenes of lightly browsed ones, and that work was done on black-tailed deer in the west rather than white-tailed deer in the east. The direction is consistent. The numbers are not transferable.

With the bones settled, theme is the next decision, and it is the one that determines whether the plant palette fights you or works with you.