Tag Archives: Winter desiccation

Water in the Winter and Antidesiccants

11-18-14 browned shrubsIf you’ve ever participated in winter sports, you know how easy it is to forget to drink water with snow around, yet once you do, you realize how thirsty you are! It is easy to get dehydrated if you’ve been outside for a while in the winter sun. Plants are no different.

When it is super cold outside, the humidity in the air drops significantly. That is what makes the air feel clean and crisp. And why you need a humidifier indoors. This dry air can cause serious damage to plants especially when combined with wind and sun. Even though it is cold outside, it can be warm inside the plant’s leaf – and water evaporates. When a plant loses more water than it can replenish through its roots, the natural process of transpiration (water loss through plant respiration) causes plant desiccation. Desiccation is when the plant cells collapse and die after drying out, causing discolored/ brown/dry areas of tissue. We call this winter burn.

Most important: we can’t prevent the soil around the roots from freezing – but we can give our plants a leg up prior to the ground freezing. Watering your trees and shrubs well into the fall, right up until the ground freezes, can help plants fully hydrate. We recommend watering through Thanksgiving. This is especially important if rain has been scarce during the growing season like this summer.

For some evergreens and bro11-18-14 dessicated rhodo leavesadleaf evergreens like Rhododendrons and Hollies, antidesiccant sprays can help. The anti-transpirant spray coats the leaves and diminishes the loss of moisture through the leaf’s pores, much like an oil based lotion on your legs. These sprays should be used in late December (temps @ 40°), only after the evergreen is fully dormant. Otherwise water can get trapped in the leaf and freeze, causing cellular damage. Our sources indicate that antidesiccants are not reliably effective and can actually harm some plants like Chamaecyparis and Blue Spruce. Read the label and follow directions carefully if you want to try it.

You may recall seeing shrubs all bundled up in burlap in the winter. This can be effective, particularly when the plant is subject to sun and wind or salt. But the cold still gets inside the burlap. We only recommend burlapping shrubs if they are in a very vulnerable location. Often these “winter tasks” are more for our comfort as the gardener looking at our plants rather than for the plant’s benefit. This is true too for salt marsh hay. We don’t use salt marsh hay for a variety of reasons – we leave a layer of leaves on perennial beds. The best “blanket” is actually snow itself, which keeps the temperature around the leaves consistent and blocks the sun.

With winters, we face the vagaries of nature and have to admit that we can only do so much to help our friends the plants.