Question of the Week Number 1: September 13, 2018
Linda G. from Cresson, TX posted this photo and question to my Facebook page recently. I get it so often regarding all kinds of plants that I decided to use it as a teaching example.
Here’s what she wrote…
“Why are my tree’s leaves brown around their edges, and why are they turning yellow early?”
I compare this situation to the human circulatory system. When we have circulation issues, the problems farthest from our hearts are where issues appear first and worst. Frostbite, for example, occurs at the tips of fingers and toes, ear lobes and the end of the nose.
The comparable plant parts – those that are farthest from the roots where water is taken into the plants – are the tips and edges of the leaves and the far ends of fruit. We discussed earlier this summer the problem of “blossom-end rot” of tomatoes when the plants wilt and the point on the far end of the fruit turns dark brown and sunken due to moisture stress at critical times.
When leaves turn brown at their tips and edges, it’s the very same thing. The plant hasn’t gotten enough water out to those tissues and they have wilted and burned.
Most common cause of this problem…
• The plant got too dry one or more times. You saw that one coming! This most often happens with new trees (and shrubs) that we forget to water in a timely manner.
But there are other possible causes…
• Too much fertilizer can cause water to be pulled out of plants’ roots (reverse osmosis), thereby robbing plant tissues of much-needed water.
• Hot, dry winds can pull water through a plant faster than its tissues can pull it up and to the leaves. That’s what happens when we try to grow plants that are better adapted to cooler, more moist locales.
• Root or trunk damage done to larger trees can cause this. It can be from transplanting, or it might be due to trimmer damage or roots cut by a trencher.
Can this be caused by excessive watering?
Usually not. In those cases the entire plant wilts and yellows simultaneously. All of its root system has been essentially drowned by water filling all of the soil’s pore spaces. All of this happening while the soil is still very wet. It’s a different set of circumstances entirely.
As for this plant’s yellowed leaves…
This has been a rough summer on many of our trees and shrubs, and many of them are responding by changing to their fall leaf colors weeks ahead of schedule. While of a bit of concern, it’s not always signs of impending disaster. This plant just got too dry enough times that it has decided to shut up shop a bit early and hope that next year will be more favorable. I think we all hope for that.