How to protect young trees from winter damage

Protect young trees in late fall, after the leaves drop and before the ground freezes. Wrap the trunk from the base to the first branches with a white plastic spiral guard or light-colored tree wrap. This stops sunscald, which cracks bark on sunny winter days. Next, circle the trunk with 1/4 inch (6 mm) hardware cloth, 18 to 24 inches (45 to 60 cm) tall, to block mice, voles, and rabbits. Water the tree deeply one last time before the soil freezes. Pull mulch back a few inches from the trunk. Remove the wrap in spring.

Short on time? Do three jobs today. Wrap the trunk, set the wire cage, and soak the root zone. Each job takes a few minutes per tree, and the first two matter most.

Which trees need winter protection

Young trees with thin, smooth bark need it most. That includes apple (Malus domestica), cherry, plum, peach, and maple trees in their first few years. The bark thickens and roughens as the tree ages, and the risk drops with it. Most growers protect a tree for its first three to five winters.

Winter injury matters more in cold zones, where snow cover lasts and daytime sun swings sharply against nighttime lows. If you do not know your zone, my post on how to find your growing zone shows how to check. Trees that are only marginally hardy in your zone need extra care beyond the steps here.

A tree planted this fall has the most to lose. Its roots have not spread yet, and its bark has never faced a full winter. Protect it first.

Stop sunscald with a trunk wrap

Sunscald is bark damage from winter sun. University extension guides on winter tree injury describe it as a problem on the southwest side of the trunk. On a clear day, the sun warms the bark and wakes the cells beneath it. After sunset, the temperature falls fast. The cells freeze and die. In spring, you see a long sunken strip or cracked bark on one side of the trunk.

A light-colored wrap reflects the sun, so the bark stays closer to the air temperature. Use one of these:

• A white plastic spiral tree guard. It is easy to put on and take off.
• Light-colored paper or fabric tree wrap. Start at the base and wind upward, overlapping each turn by about one third.
• Water-based white latex paint thinned with equal parts water. Brush it on the trunk. Do not use oil-based paint.

Cover the trunk from the soil line to the first main branches. Keep the wrap snug but not tight, because the trunk will keep growing. Avoid dark wraps and black plastic. They absorb heat and make the problem worse.

Put the wrap on in November, once the leaves have fallen. If you are reading this in early November, you are on time.

Keep mice, voles, and rabbits away

Small animals chew bark in winter when other food runs short. Voles and mice work under the snow, where no one sees them. Rabbits chew at the height of the snow line. If an animal strips the bark all the way around the trunk, the tree cannot move water and sugars between roots and leaves. This is called girdling, and it often kills young trees.

A wire cylinder stops it. Buy hardware cloth with 1/4 inch (6 mm) mesh. Cut a piece long enough to circle the trunk with a gap of an inch or two (3 to 5 cm) between wire and bark. Make it 18 to 24 inches (45 to 60 cm) tall. Push the bottom 2 to 3 inches (5 to 8 cm) into the soil, because voles tunnel in from below. In snowy areas, choose the taller size, since rabbits stand on packed snow.

A plastic spiral guard also blocks gnawing, but wire holds up better against voles. Some growers use both.

Check the cylinder after each heavy snow. Stamp the snow down around the trunk to firm it. Voles dislike travel across packed snow.

Pull back the mulch

Mulch protects roots, but a thick pile against the trunk gives voles a warm place to nest and chew. Lay 2 to 4 inches (5 to 10 cm) of mulch over the root zone and keep it 3 to 4 inches (8 to 10 cm) away from the bark. My post on mulching tips covers depth and materials. If wind moves your mulch around, how to keep mulch in place helps.

Shredded leaves work well as winter mulch. While you rake, my fall yard clean up checklist can help you plan the rest of the work. Remove fallen fruit and leaves that sat under diseased trees. Do not mulch with them.

Water before the freeze

Dry roots suffer more in winter. Water young trees deeply every week or two in fall if rain has been light. Keep going until the ground freezes. Soak the whole area under the branches, not only the base of the trunk.

Moist soil also holds heat longer than dry soil. That gives the roots a small buffer on the coldest nights.

Stop fertilizing in late summer. Fertilizer pushes soft new growth, and frost kills that growth. For feeding plans in the growing season, see my guide on how to grow apples.

When to take the wrap off

Remove spiral guards and tree wrap in spring, after the last hard frost. For most cold zones, that means April. Left on all summer, a wrap traps moisture against the bark. Insects and disease then move in. Wire cylinders can stay if they have room for the trunk to grow. Check the gap each year and widen it as needed.

When you take the wrap off, look at the bark. Healthy bark looks smooth and tight. A sunken, cracked, or peeling strip means winter injury. Do not paint the wound or pack it with sealant. Let the tree heal on its own and protect it better next winter.