Homegrown Column July 04, 2009

Our 8-year-old redbud has loose bark at its base. I’ve peeled some off and don’t see any pests. I’ve removed river rock to give it more “air.” Should I be worrying? 
— Pat

Does the tree look good overall? If it’s leafing out well and growing fine, I wouldn’t be too concerned.

The dead bark could be due to a number of causes, from sun scald to “lawn mower blight.” There’s even a chance that what you’re seeing is simply the natural bark maturation process of the tree where the smoother juvenile bark transitions to the thicker, more scaly (and peeling a bit) mature bark.

You could check to see if that is what is going on by sticking a pocket knife blade into the tissue beneath where the bark is peeling.

If there’s moisture in that tissue and it’s greenish or whitish, then the tissue is alive and fine.

If the tissue is hard and dry (like sticking the blade into a two-by-four) then something killed that area of bark.

If that’s the case, again we’re faced with the question “what did it?”

If the tree is leafing out well and there’s no oozing or other weird goings on there, then I’d chalk it up to a random, one-time incident.

The focus from here on out is to treat the tree as well as you can.

Make sure it’s being watered deeply but infrequently and be very sure to water the tree occasionally over the winter. Redbuds seem to be very prone to winter drought damage if they’re not watered.

If the tree is in the lawn, clear the grass away from the base of the tree. Not only will this make it faster to mow, it should eliminate the possibility of physical injury to the bark when the mower bangs against the tree.

Other than that, just treat the tree as if there’s nothing wrong and it will plug along and heal the damage that’s there. However, if there are other things going on, such as oozing or dead branches, then we’ll need to talk a bit more.

What interval would you consider successful/acceptable between routine, regular spraying of apple trees and a rain? For example, if it rains one hour after spraying, should
I consider the whole spray a waste and reapply? The apples also get some sprinkler water, but I try to wait at least a couple of days after spraying.
— Ed

I’m afraid there’s no cut and dry answer about your question of rain.

There are a lot of factors involved in whether a respray is necessary or not. Perhaps the most critical is the amount of rain.

A light sprinkling, which is more the norm around here, shouldn’t affect spray efficacy too much.

A heavy, sustained downpour will obviously have a greater impact.

Associated with the rain is how exposed the part of the plant that was sprayed was to the rain. Something on the upper surface of the leaf will obviously be impacted more than the underside.

Trunk sprays are usually not affected that much because the foliage of the tree usually directs the rainfall outward toward the margins of the canopy.

It’s not until a heavy and sustained rain occurs that the bark will become soaked.

Another factor is the interval between spraying and rainfall. The longer the interval, the more effective your spray will be.

The properties of the specific chemical used will also have impact on its effectiveness. Some chemicals become “rainfast” more quickly than others.

The answer to your question is to aim for as long of an interval as possible.

If it’s calling for a pretty good chance of rain for the next couple of days, it might be prudent to hold off until that passes. However, if the situation is critical, where the plant could suffer significant harm, then I’d probably go ahead and take my chances and spray, risking the chance that I’ll have to reapply it.

Dennis Hill is the nursery manager at Bookcliff Gardens, online at http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail info@bookcliff


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