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Lichen on the bark may be a sign of a deciduous tree under stress, but not necessarily. Photo: tobascodagama via Flickr
Lichen on the bark may be a sign of a deciduous tree under stress, but not necessarily. Photo: tobascodagama via Flickr

Helping stressed-out trees

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According to Cornell Cooperative Extension's Amy Ivy, it's hard to do a whole lot to "heal" a sick tree, but in her conversation with Martha Foley, she offers some common sense tips on keeping healthy trees strong. There are also ways to slow the progress when a tree is in decline.

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Reported by

Martha Foley
News and Public Affairs Director

Amy Ivy says that the Cornell Cooperative Extension has been receiving phone calls about trees lately. They’ve also been brought a variety of long tree branches, which are great specimens for the staff at the office to study. Trees have become a topic of discussion lately because concerned owners worry that their trees are unhealthy and are unsure of how to properly care for them.

“This is the time of year I think when trees are really trying to push out the new growth, when you can really get a sense ‘oh my goodness, that beautiful tree that I love so much isn’t doing well,” said Ivy. “It shows the symptoms more dramatically this time of year when everything else is so lush and growing like crazy.”

The wide variety of symptoms that trees can show makes them complex patients to diagnose. Some people notice that the leaves on their trees are much thinner than usual, or are failing to appear on entire branches. Ivy said, “What’s really challenging is when the tree trunk is covered with lichens or has big splits that just haven’t been healing well.”

According to Ivy, the majority of the questions she receives concern shade trees. These include maple, ash and oak trees. However, the queries can also apply to evergreens that occasionally change color from green to orange in the spring. “That’s not a good sign for them to be turning orange this time of year,” said Ivy.

“The thing with trees is that they respond really slowly. The damage that people are noticing now or the suffering that the trees are showing now probably has been occurring for five to 10 years,” said Ivy. “That’s what’s so hard about that; you’ll have a good year and a bad year, and that kind of thing.” Trees have a high tolerance for abuse and an ability to hide symptoms for years.  As a result, answering questions about them can be difficult.

“I remember we had terrible droughts in the 90’s, and then we finally got some rain. There was this one rainy summer and I got more samples and I had to say, ‘this tree is dying from drought,’” said Ivy. Given the flood conditions at the time, it was difficult for the owners of the tree to believe, but successive years of drought had caused significant damage to the trees.

Lichens are commonly seen on local trees such as maples. Though these gray or green amoeba-shaped organisms don’t cause any harm to the tree, they are evidence that the tree is unhealthy. “As a tree starts to decline, it doesn’t grow as much,” explained Ivy. “The trunk on a healthy tree continues to get broader and broader, it’s moving and growing. And when a tree is under stress, now it’s not increasing in girth nearly as much.” As the tree becomes more like a stationary object, such as a rock, it provides a better habitat for lichens.

Unfortunately, trees are difficult to treat. Ivy said, “That’s what’s so frustrating and heartbreaking because it’s hard to turn it around with a tree, especially because the damage probably started five to ten years ago.”

“The most important things people can do if they expect their tree is suffering, if it’s a tree they value, they should call in a trained arborist,” said Ivy. Arborists would have taken courses on tree health and tree care and may be able to offer a professional assessment of what is causing a tree to be unwell. They can also offer advice with regards to pruning, which can often help.

“About the only other thing is to water, and it seems crazy to water a great big tree, but if we do have an extended drought, giving them water will really help to relieve a stress as opposed to doing anything else,” said Ivy. Fertilizing the trees doesn’t make a huge difference, and trees simply need their basic needs met without interference.

Many of the oldest trees in the North Country, such as maples, were planted at the same time over 100 years ago. They were originally planted alongside small, country lanes. These have since been developed into larger roads and highways that impede the routes of the trees, and have pushed them into a decline. The roots of big trees go well beyond the branches and are sensitive to having heavy objects such as cars sitting on top of them, so Ivy advised that care be taken around them.

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