Winter burn is exactly what it sounds like: damage that looks like heat or frost scorch but is actually caused by dehydration. It shows up in late winter and early spring as brown, crispy leaf edges or needles. It is often worst on the windward side of the plant or the side facing afternoon sun, where moisture loss is greatest. Plants most commonly affected include broadleaf evergreens like rhododendrons, boxwoods (Buxus), holly (Ilex), arborvitae (Thuja), false cypress (Chamaecyparis), and newly planted trees and shrubs of any type.
Here's what's actually happening: your plant keeps breathing out moisture through its foliage all winter long slowly, but steadily. When the ground is frozen, the roots can't take in water to replace what's being lost. So the plant reaches into its reserves. A plant that went into winter well-watered has something to draw on. A plant that went in already thirsty runs out and the foliage pays the price.
Deep, consistent fall watering is the most effective thing you can do to prevent it. It's also the most overlooked, because the damage doesn't appear until months later and by then, most gardeners have long forgotten what their Fall watering habits looked like.
For broadleaf evergreens in particularly exposed locations like windy spots, south or west-facing beds you can something called an anti-desiccant, like Bonide Wilt Stop®. When applied in late fall it provides an additional layer of protection by coating foliage with a natural pine resin film that reduces moisture loss through winter. It's a companion strategy to good fall watering, not a substitute for it. But for vulnerable plants in tough spots, it's worth knowing about.
