Plant Health Alert – Caring for Aging Trees

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In our work here as plant health specialists, we get images like the one below sent to us daily. People ask why their plants do not look as healthy as they should? In this case, these are high-grafted weeping cherries that I would guess are 25-40 years old. You can see where they were grafted about four feet off of the ground.

weeping cherry trees

Over-mature trees are like any organism that gets near the end of its life; old trees get less able to resist pests such as insects and disease, extremes in weather and all of the other things that can harm tree health. These particular trees are near the end of their lives. The average lifespan of a landscape tree is 25 years. Trees in landscapes live shorter lives than their wild counterparts due to the many things that we do to harm the trees.
Burying Plants Too Deep
Sometimes plants are buried too deep at planting. You should be able to see the root flare at the base of the plant. Burying plants too deep at planting or burying them too deep in mulch causes root suffocation which leads to girdling roots. In the case above, The tree in the rear of the image above is buried too deep in mulch. Both trees should have the mulch pulled back from the base of the trunk.
Lawn Care vs. Tree Care 
Think about this: Does your lawn service apply herbicides to the turf that kills broadleaf weeds? Let’s do a thought analysis. Where do we think the tree roots are? They are under the grass, correct. Isn’t a tree a broadleaf plant? Yes it is. So it makes sense that lawn herbicides might not be good for trees. Just because lawn herbicides do not kill trees doesn’t mean it doesn’t negatively affect tree health especially when lawn weed killers are applied year after year over the root zones of landscape trees.
Modern commercial lawn mowers weigh 700+ pounds; 900 with a rider. What effect do we think these gigantic mowers are having on soil compaction and root health? The mowers crush roots and compact soil. Roots need to be able to ‘swim’ through the soil to get to nutrients. Soil compaction inhibits tree roots’ ability to forage. Mowers should be kept away from trees’ critical root zone. This area is a circle from the outer edge of the branches to the trunk.
Prolonging the Life of Over-mature Landscape Trees
All you can really do to help over-mature trees is to prolong their time by making them as healthy as possible. Gardeners can make sure the soil around the tree is limed to the correct pH, fertilize the trees and prevent further harm from human activites. Plant health is like human health; a holistic approach should be applied to giving the tree what it needs (sunlight, nutrients, water) and to avoiding doing things that harm the trees (over-mulching, damaging roots with mowers and herbicides, etc.) so that the trees can thrive.
We as a society are unnecessarily harming our trees which are critical infrastructure in our communities. We are only stewards of the homes and gardens that we inhabit. Let’s invest in the future by caring for landscape trees today. If you want a professional to care for your trees and shrubs, there are many fine companies that do great work managing tree health locally. Contact me for a list of local tree care providers.