Protect Evergreens in Winter with Anti-Desiccants

Worried about your shrubs surviving winter? You can take some easy precautions to ensure that your evergreen plants survive freezing weather and winter storms and are ready for spring. Anti-desiccant treatment offers a safe and efficient way to get your greenery through winter’s worst weather. Protecting your investment (your shrubs and trees) is always a good idea, and this article will explain how.

Plan Ahead for Winter

It may be fall now, but winter is heading our way, making this a good time to develop a plan for protecting your woody perennials and trees over the cold months ahead. That plan should include:

• general winter tree and shrub care (see our winter tree and shrub care tips for details on good practices, such as mulching and watering for winter protection),
• preparations to deal with ice-covered trees, and
• protecting your evergreen plants from dehydration (also called winter burn or desiccation) by applying an anti-desiccant.

What are anti-desiccants?

Anti-desiccants, also called anti-transpirants, are surface sprays that help preserve evergreen foliage from excessive winter drying. During winter dormancy, many trees remove or reduce water from their internal tissues because they are not actively growing above ground. While drier internal plant tissue can protect trees and shrubs from winter freezing and rupturing, it can damage evergreen foliage. The damage can be especially severe when combined with road salt, drying winds, and leaf scorch from the reflected glare of snow.

Which plants benefit from anti-desiccant sprays?

There are several types of evergreen trees and shrubs that you may want to treat with an anti-desiccant.

Anti-transpirants can be particularly helpful for broadleaf evergreens, such as:

• Hollies (Ilex species)
• Rhododendrons
• Boxwood (Buxus species)
• Laurels (Prunus laurocerasus)
• Japanese pieris or Andromeda (Pieris japonica)

They are also beneficial as winter protection for coniferous evergreens such as:

• Yew (Taxus baccata)
• Pine (Pinus species)
• Arborvitae (Thuja occidentalis)

IMPORTANT: Do not treat evergreens that have waxy coatings on their needles, such as blue spruce (Picea pungens), with anti-desiccants. Always check the recommended species and warnings before applying, and always learn about your choice of anti-desiccant spray before you start to apply it.

How do anti-desiccants work?

Anti-desiccant sprays work by preventing the normal release of water from leaves and needles. Although your plants and trees are dormant in winter, evergreen shrubs and trees are still transpiring (releasing water through their leaves). This is part of their normal function, although they do it at a greatly reduced rate in winter compared to the growing season. Think of it like hibernating animals; even while deeply asleep they’re still alive and breathing, but so slowly that it’s hardly noticeable.

How are anti-desiccants applied?

Anti-desiccants are generally sprayed on the plants they’re intended to protect. The sprays contain waxes that coat the exposed surfaces of foliage and need to be uniformly and thoroughly applied in order to work.

When should an anti-transpirant spray be applied?

It’s important to apply sprays to evergreen leaves or needles correctly and at the right time. The best time to apply an anti-desiccant spray is:

• In late fall, before freezing weather sets in (and before the soil freezes)
• Before snowfall
• When the weather is clear but not hot, around 40 to 50 degrees
• When there is no recent rain or wet foliage
• There is no rain expected in the immediate future

Note: For mild falls and winters, wait until dormancy has completely set in before spraying. It’s harder to tell with conifers when they have gone fully dormant, and you don’t want to smother their needles if they’re still actively transpiring.

Winter damage on a broadleaf evergreen that was not treated with anti-desiccant

How many applications are needed?

Anti-desiccants may need to be applied several times during the winter, depending on weather cycles. Since the sprays are not intended to be permanent, they degrade over time. Heavy rain and periods of warm weather can speed their disintegration, so an application in November may need to be repeated in January or February.

Is using an anti-transpirant enough to fully protect my plants?

Winter dehydration or desiccation of evergreens can be severe and can kill plants. Even with the application of anti-desiccant sprays, trees and shrubs will benefit from supplemental irrigation to ensure that they have enough moisture.

Water your plants in winter if there is an extended period of dry weather and temperatures that reach above freezing. Always irrigate early in the day, after temperatures have risen and before they drop in the afternoon. That way, the slowly warming soil has a chance to absorb the water and send it down into the soil where plant roots are.

Should I do anything else to protect my broadleaved evergreens?

In addition to anti-desiccant sprays, you may want to protect any evergreens in exposed locations from strong winds. Burlap wraps and windscreens are effective and may be needed in places where an anti-desiccant spray does not provide enough protection.

You’ll probably also want to protect plants from corrosive and damaging road salt. If you have evergreens that are exposed to road salt spray, plant wraps can offer additional protection. During warm spells, extra irrigation to those plants is also beneficial. You may want to wash off the road salt by hosing down your wrapped or unwrapped plants, but don’t do it if temperatures will drop to freezing before water droplets have evaporated. A coating of ice can be protective but it can also damage leaves.

>> Learn how to prevent winter salt damage to your plants

A Final Word

We offer winter protection services for your trees and shrubs. If your yard is too large for you to do all the work to protect your plants from winter weather, give us a call and we’ll take care of it for you. Trees and shrubs, especially mature ones, are more valuable than you might think, so protecting them is a wise investment.