Lichens Take a Likin' to Canon-Mac Area Trees

Some trees in the area are going greener—in a way that some homeowners might not find aesthetically pleasing.

In the Pittsburgh region, there are trees sporting green patches that, while interesting from an artistic or scientific perspective, can bother those who like their landscaping to be perfect.

The culprit? Lichens.

"It's actually a pretty interesting thing," said Brian Wolyniak, an urban forester with Penn State Extension's Allegheny County office in Point Breeze. "It's really a couple of organisms living together."

A fungus creates a flaky-looking patch on the tree bark, Wolyniak said. Then algae, which lives symbiotically within the fungus tissue, gives the organism a green color.

Lichens prefer cooler, more moist environments—why they are mainly seen growing on one side of the tree. Given the wet conditions we have this summer, they are "probably flourishing ... doing very well," according to Wolyniak. Over time, they can fade, and then return based on weather and sunlight.

The good news is that lichens are harmless.

While, aesthetically, lichens might "not look great," he said the growth can be left alone.

However, for those homeowners who don't want it growing on the tree bark for appearances, it is fairly easy to remove. Lichens can be removed by scrubbing with a little soap and water—or using a fungicide. 

"It attaches pretty loosely to the bark," Wolyniak said. "The trick is to be careful not to damage the bark."

When using a fungicide, a homeowner needs to pay attention to the details for using the product, such as applying it at the right time of the year. There is a cost involved to purchase the fungicide, where the soap and water are inexpensive, he said.

"I do not recommend using chemicals for something that's truly an aesthetic reason," Wolyniak said.

There is a plus-side to seeing lichens in the area—and that has to do with our air quality.

"Their abundance and diversity can be an indirect assessment of air quality and habitat alteration in an urban environment," according to the Opdyke Environmental Lab website.

The lab, conducted by Matthew R. Opdyke, an associate professor of environmental studies at Point Park University, is studying the application of lichens as biological indicators of air quality in southwestern Pennsylvania. 

This project started in 2008—with the support of a Pennsylvania Department of Conservation and Natural Resources, Wild Resource Conservation grant—to study the application of lichens as indicators for habitat alteration and air pollution in southwestern Pennsylvania. Partners on the project included Pittsburgh Parks Conservancy and the New York Botanical Gardens. 

The study sites included Schenley and Frick parks in Allegheny County, Mingo Creek Park in Washington County and Roaring Runs Natural Area (Forbes State Forest) in Westmoreland County. 

Researchers measured lichen density and diversity at each park to investigate the prevalence of sensitive and pollution-tolerant species. The information will be used to assess the health of the lichen community, which reflects the level of air pollution and urbanization in the region, the website says. 

Although the five-year surveys will not occur again until 2014, there are currently projects that involve examining lichen distribution on islands in the Allegheny River.

For more on lichens, click here for story by Opdyke's wife, Heidi Opdyke of McCandless, that appeared in the Pittsburgh Post-Gazette in 2011.

Do you have lichens growing on your trees? Have you attempted to remove it? Let us know in the comments below.