Plan ahead next year to avoid leaf scorch

Leaf scorch is primarily caused by a lack of watering during the wintertime or springtime over-fertilization. The bad news is that once you have it, there’s nothing you can do about it. Those dead tips and crunchy burnt-looking leaves are irreversible. However, there are things you can do to avoid leaf scorch next summer.

Sometimes diagnosing gardening problems requires foresight, hindsight and a little detective work. And though it might be hard to believe, a cause and effect can often be months or even years apart in the timeline of events in your landscape.

Lately, I’m seeing a lot of evidence that people didn’t water their trees and shrubs back in January, or they overwatered them earlier this summer. You might wonder how the heck that sort of thing is apparent in August, but believe me, the evidence is overwhelming.

The smoking gun here is called leaf scorch. It looks exactly how it sounds — like the leaves on your tree, shrub or even a rose bush were burnt to a crisp around the edges. It might start at the very tip or evenly start around the edges, moving toward the center of the leaf. In some severe cases, an entire leaf gradually turns brown or black and crunchy, dying on the stem. The easiest examples to see around town are usually on aspen trees, which really have a hard time surviving at our elevation and climate.

Here’s the bad news about leaf scorch: Once you have it, there’s nothing you can do about it. Those dead tips and crunchy burnt-looking leaves are irreversible.

But, you can plan ahead to avoid this problem next year. Your neglected plants can recover with a little help.

In our part of the country, leaf scorch is primarily caused by a lack of watering during the wintertime. Another cause can be over-fertilization. If you got a little overzealous with the fertilizer tree spikes in the springtime, that could be the culprit.

It also could be a result of watering so much that the roots are drowning in moisture. The damage occurs over time and is tied to damaging the roots of the plant so much that it cannot absorb water or nutrients properly.

Why do we see leaf scorch rearing its ugly head months after the problem occurred?

A little bit of plant biology helps to understand this. In Colorado Master Gardener class, we learned that the fine root hairs on plants are crucial to plant development. Sure, roots help anchor plants in the ground, and we know they absorb water. But the very tips of those roots are where all the action happens for taking up nutrients, minerals and even oxygen. (Yes, roots breathe! Isn’t that crazy?)

Without getting into the complicated particulars, if these root hairs are damaged, that’s bad news for the plant. You will start to see the effects of this over a period of time, depending on the severity.

Watering properly (at the end of the root tips, under the edge of the branches, not with a hose shoved up against the trunk of a tree) and on the correct schedule (at least once a month in the wintertime, when temperatures are above freezing and there’s no snow on the ground), will help prevent this problem next year.

Avoiding overwatering, and fertilizing judiciously will help. The worst cases of leaf scorch seem to be a combination of lack of watering in the wintertime and drowning plants in the summertime.

Moderation is key here, folks. Maybe you’re wondering how to tell if you’re watering too much. Your best tool is observation and your own hands. Get down there, and feel around the soil at the base of your plant and at the edge of the root zone. Is it sopping wet? Bone dry, hard clay? You’re looking for something in between, where you can push the soil into a clump when you make a fist with it.

Everyone’s yard is different, with different soil conditions, and exposure to full sun or part shade makes a difference. A tree planted in a lawn might get more or less water than it needs, just from your sprinkler system. Maybe your shrub is located next to your paved driveway and can’t get water through the soil on one side. Or perhaps your tree’s root system grew mostly into your neighbor’s yard and needs watered over there — let’s hope you have a friendly neighbor who cooperates — or maybe your neighbors water their yard incessantly and you should cut back on your side.

The bottom line is you have to be the best judge of how much to water your landscape. There’s no silver bullet here. Just use your powers of observation to deal with your particular situation and all its quirks. It could mean the difference between a healthy or sad-looking plant in the future.

Erin McIntyre is an advanced master gardener, writer and Grand Valley native. Please email her at .(JavaScript must be enabled to view this email address) with story ideas or feedback.


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