We always receive a lot of questions about landscape plants, but over the last several weeks concerned clients from across the state of Iowa have posed the same question…what's wrong with the leaves on my shade trees? It started with maples, now we're seeing similar symptoms on other species of landscape trees.
What are the most common symptoms?
Limp, desiccated leaves with a water-soaked appearance, often with some necrosis (dead tissue) throughout. Newly expanding or recently formed leaves that have not yet developed sufficient thickness, and protective waxy coatings are the most likely to show symptoms.
What's the cause?
We think strong and sustained winds are the most likely culprit. Our confidence in this diagnosis is strengthened by the fact that injury symptoms have been noticed on many individual trees within the same genus (maples) but also across several other genera and species. Plant pathogens that cause diseases are host-specific, meaning they are picky about which plant species they will cause disease on. Similar symptoms appearing at the same time across many types of plants is a telltale indication of abiotic injury. In this most recent case, the unfortunate coincidence of strong and sustained winds with vulnerable foliage seems to provide the most logical explanation for injured leaves on landscape trees.
What should you do?
One of the great things about trees is if they are happy and healthy in the landscape, they should have enough energy reserves to push out new leaves to replace the dried, sad leaves that will eventually fall off. So, you need not do anything but watch and wait.
What about the long-term vitality of the tree?
If trees are happy and healthy in their landscape, their long-term vitality should not be impacted. This does warrant a reminder of the importance of managing the stress of landscape trees for long-term health, though. I've been directing many clients to two writeups from University of Massachusetts Amherst:
Long-term Drought Effects on Trees and Shrubs
Helping Trees to Manage Stress
These writeups reinforce the idea of proactive landscape management to limit the stress of landscape trees and plants and give them the best chance at a long and healthy life.
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