Is Rhododendron deer resistant?

Evergreen leaves make the whole genus a winter browse target, and where deer are resident an unprotected rhododendron will be stripped as high as they can reach. All species need acid soil that holds moisture but drains sharply, which is why they fail in clay. Every part is toxic.

Do deer eat rhododendrons?

Yes, and reliably. Rutgers rates the genus Frequently Severely Damaged, the bottom tier, in the company of hostas, yews and azaleas, and NC State's entry is two sentences long on the point: "This plant is frequently damaged by deer." "Deer browse this plant." The big evergreen leaf is winter food, held on the plant through the months when nothing else is, and the flower buds sit at the branch tips through the same months at exactly the height a deer feeds. The grayanotoxins that put rhododendron on every poison list do not stop it: NC State rates the poison severity Low and notes that "ingestion of moderate amounts of azalea (nectar or leaves) poses little toxic hazard," and a deer's tolerance is evidently higher than that.

Are any rhododendrons deer resistant?

None in the top two tiers. The native species do a little better than the hybrids on the Rutgers list: Carolina, Catawba and rosebay rhododendron are all Occasionally Severely Damaged, one tier up, and deciduous azaleas are the same. Evergreen azaleas and pinxterbloom are the bottom tier with the genus. For the evergreen mass a rhododendron gives under trees, the shade page names the substitutes: pieris, leucothoe, plum yew, inkberry, mahonia.

Protecting rhododendrons

A rhododendron that matters is fenced or wrapped every winter, from November to April, for as many winters as it takes to grow past reach. In the VerCauteren trials a 1.5 meter fence stopped none of the deer, 2.1 meters stopped 85 percent and 2.4 meters all of them; a wire cage around one shrub is the cheap version of the same arithmetic. Repellent works on a small planting and has to be renewed through the winter: Colorado State's 20 percent egg spray is rated High at about thirty days, which is five applications between leaf drop and bud break. The ASPCA lists rhododendron as toxic to dogs, cats and horses; the callout below carries it.

If it is browsed

Next spring's flowers were set last summer at the tips, so a winter browse takes the bloom even where the shrub lives. A rhododendron eaten back to bare wood may or may not break new growth from it, and the ones that do take years to look like a shrub again. Ten years of growth is the usual price of one unfenced winter, and the money is better spent on the fence.