This fall, seasonal needle drop on white pine trees -- including this tree on the Belfast Rail Trail -- may be much more visible than normal because trees were stressed during the drought in May and June. Credit: Abigail Curtis / BDN

BELFAST, Maine — This fall, if it seems that white pines have an unusual amount of yellow, orange and brown needles that are about to drop, it’s not your imagination.

Evergreens usually drop some of their older needles in the fall, but the severe drought in May and June may be causing stressed trees to shed more needles than they normally would, according to Aaron Bergdahl, a forest pathologist with the Maine Forest Service.

He has heard reports of stressed-looking white pine trees in southwestern Maine, central Maine, the midcoast and Aroostook County, and believes it is likely to be a statewide phenomenon. In Belfast, people recreating on the popular Belfast Rail Trail may have been startled to see pine trees that look almost as orange as green because of all the orange and brown needles.

“I’ve gotten a couple of ‘All the pine trees are dying’ phone calls,” the forest pathologist said.

The trees aren’t dying — but they can look distressing.

“The truth is, it’s a natural process, but it looks a little worse this year,” Bergdahl said.  

The eastern white pine is the tallest tree in eastern North America and holds an equally massive place in both Maine’s natural landscape and human history. It’s the official Maine state tree and the inspiration for the nickname of the Pine Tree State, but despite its lofty size and stature in our hearts, it is not immune to climate-related stressors.

According to the natural way of things, in the fall, eastern white pines drop their older needles because those needles use more energy for the tree to “defend and maintain,” he said. Usually, the needles that drop are the ones that were new three years ago.

This year, the trees may be losing both their second and third year needles in order to conserve more energy.

It’s a sign of drought stress, Bergdahl said, but it isn’t a disease. During the spring months, trees generally grow the most, but this year there wasn’t enough moisture in the soil to support the growth.

This white pine tree that grows alongside the Belfast Rail Trail looks almost as orange as it is green. Credit: Abigail Curtis / BDN

“We had a terrible, terrible drought in May and June,” he said. “Then it rained in July and people forgot. Trees have a different time scale. Trees don’t forget.”

During a drought, the finest, thinnest roots in the soil tend to die back first, he said.

“They’re the most fragile,” he said. “They’re also the best at absorbing nutrients in water.”

The tree needs to regrow those fine roots, but in order to do so, it expends a lot of its energy, meaning that there isn’t a lot left to maintain older pine needles.

“To look at the year in the tree in terms of an energy budget, the tree is definitely in the red in the spring after that drought,” he said. “The tree is running at a loss. Therefore, fall needle drop is maybe more severe than usual.”

He is seeing it in a lot of white pines and in white cedars as well. But pine trees are the trees that people notice.

“I have started to get the calls, and I anticipate that more will be coming,” he said. “In areas where the trees have been a little bit more stressed, they’re going to show a little bit more of the seasonal needle drop.”

But even though the trees may look sick or unusual, it’s not a disaster for them, he said.

“Not to give the tree human-like decision-making capabilities, but the tree is doing this for its own benefit. It’s doing this to get rid of tissues that are sort of not carrying their own weight,” he said. “It’s an economic reaction to the environmental conditions.”

Still, it’s not ideal for the trees, which are just doing their best to cope with changing climate conditions, Bergdahl said.

They also have been contending with a disease that does cause the trees to lose their needles prematurely. White pine needle disease is a complex of fungal diseases that cause early defoliation earlier in the year, in June and July.

Unlike what is happening now, it’s not a natural process. It has been occurring every summer in Maine for the last 15 years or so.

“We have had very wet springs,” Bergdahl said. “It’s allowed this disease to creep up and get really big. It causes the needles to turn yellow in June and fall off the tree. It’s become so common that people don’t even call about it.”

The state’s changing weather patterns can be hard on our trees, which like for things to not be so extreme, he said.

“They like to have periodic rains of normal amounts, and temperatures that are not fluctuating,” Bergdahl said. “Quite honestly, our climate here in Maine has unfortunately seen some pretty unusual weather patterns. Trees are trying to adapt to that as best they can, but it does cause some stress.”