Antidessicants for Broadleaved Evergreens
Last winter I never got around to spraying my rhododendrons with an antidessicant. The result was the rather pitiful looking Rhododendron ‘Cunningham White’ shown in the photo at right. Although it survived, and even bloomed, it lost about 20% of its leaves to winter damage and now is rather mis-shapen. Rhododendrons can be susceptible to cold damage if they’re not in a protected area, don’t receive regular or sufficient water over the winter, and/or have inadequate mulch or soil covering their roots. Mine’s in a perfect location from design perspective, but not such a perfect spot in terms of winter protection. And, since I’m a somewhat lazy gardener, I don’t always provide the temporary winter protection that would help it get through the winter with a full set of dark green, glossy leaves and unblemished flower buds. That’s where the antidessicant comes in.
In late fall, many gardeners spray their evergreens with antidesiccants (also called antitranspirants). Why? To stop or reduce the amount of water lost through the leaves during the winter when the ground is frozen and the plant cannot take up enough water through its roots. But, if your prized rhododendron or pieris isn’t sited in an ideal location, an antidesiccant may make the difference in spring between a healthy and floriferous plant or one that’s shriveled and brown along the leaf margins.
Always read the directions carefully before using an antitranspirant (such as WiltPruf). Some plants should never be sprayed with these products, including plants with a bluish waxy leaf coating. This coating is a natural antidesiccant that is washed away when sprayed with man-made antidesiccants, along with the bluish color. Only spray when temperatures are above freezing. The best winter protection is achieved by spraying in late fall (here in southwestern Connecticut it’s not too late to spray as temperatures are still quite mild – in fact, I just sprayed mine yesterday) and again toward the end of winter (on a warmer day). The thin coating of antitranspirant should help your evergreens reach spring in prime condition.