Q: I had a lot of plant damage this winter. I'm wondering if it would've helped to spray Wilt Pruf on them. Do sprays like that prevent winter damage?
A: Wilt Pruf is a popular brand of a type of spray known as an antitranspirant or antidesiccant.
They're primarily resin, latex or wax that coat leaves and block their pores (stomata). The idea is that the coating slows moisture loss from the plant.
In the case of winter injury, the products claim to decrease the leaf and needle browning that can results from a combination of cold, drying winter wind and frozen soil that prevents plant roots from replenishing that lost moisture.
Research and claims conflict over how well antitranspirants do that. Most of the field studies into winter damage show they have little to no effect on that front.
I'd have to agree. Even if you apply the sprays three times over winter as usually is recommended, they make only a slight difference at best, from what I've both seen and read.
Especially this winter in which the frigid wind blew so much, the soil stayed frozen for so long, and the temperatures yo-yo'd back and forth so often, I doubt that antitranspirants would've prevented the widespread plant browning and deaths we saw.
Just getting the spray on was a problem. Directions say antitranspirants should be applied in winter only in above-40-degree conditions. This past winter, we went weeks without seeing that, rendering the sprays useless.
A better (and cheaper) way to head off winter windburn is to make sure the ground is moist heading into winter and to have a 2- to 3-inch layer of mulch over the ground.
It also helps to stick with plants that are plenty cold-hardy to our region and to keep borderline-hardy species – especially the most moisture-losing broadleaf evergreens – in wind-protected sites.
Evergreens in pots are even more prone to winter drying injury, but they can be moved along heated walls, into a garage or to a wind-protected spot to help them weather winter.
A burlap wind barrier is another option. Hammer stakes a few inches out from plants you're protecting and staple the barrier to the stakes to make a protective wall. That's a better approach than wrapping the burlap right onto the plants.