UF study says trees not only beautify highways, they can calm motorists down

Trees not only beautify highways, they can calm motorists down, says a University of Florida scientist. Furthermore, according to new UF research, the trees planted along Florida’s highways survive remarkably well, even after a period scientists call “transplant shock.”

“Beauty and stress relief are probably the two most meaningful benefits trees bring to highways,” said Andrew Koeser, an assistant professor of environmental horticulture with the UF Institute of Food and Agricultural Sciences.

“The trees enhance the experience of both tourists and residents as they drive to their destinations,” Koeser said. “Additionally, there is research that shows folks who drive along tree-lined roadways have less stress compared to those navigating the concrete jungle without that green breakup.”

Recognizing these advantages, the Florida Department of Transportation (FDOT) transplants many kinds of trees along the state’s highways, including palms, the variety most widely associated with the Sunshine State. Indeed, about 51 percent of the transplanted trees are palms. The rest include crape myrtles, buttonwoods and many other varieties.

To assess the success of its tree-planting program, FDOT awarded Koeser grant funding to study how well the transplanted trees survive and thrive.

Koeser and his team surveyed 2,711 trees along rural and urban stretches of the state’s highways. They found that more than 98 percent “established” themselves. That’s another way of saying the trees have survived the hardships of planting and are growing into the surrounding landscape.

“The establishment rate is among the highest on record,” said Koeser, a faculty member at the UF/IFAS Gulf Coast Research and Education Center in Balm, Florida.

For instance, the success of Florida’s highway tree transplanting program rivals that of a program in East Palo Alto, California, which had a 96 percent establishment rate. Florida’s program also

compares favorably to survival rates of trees in many transplanting programs along highways and urban areas worldwide, according to a 2014 study Koeser led.

FDOT contractors are responsible for tree maintenance, including watering, mulching, creating berms around trees to keep water close to roots and more. The FDOT inspects the contractors’ work.

“Since the contractors say they will deliver what is promised, they are more eager to do the care needed to get the trees through the period of stress we call ‘transplant shock,’ ” Koeser said.

Koeser’s study is published in the journal Urban Forestry & Urban Greening.