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Good results from Florida’s urban tree-planting program, UF/IFAS study shows

GAINESVILLE, Fla. — Florida’s urban tree-planting program works well: 93 percent of the trees planted were still alive up to five years after they were planted, a new University of Florida study shows.

UF researchers attribute the high survival rate to the state’s rules for projects funded as part of its Urban and Community Forestry Grants program.

Run by the Florida Forest Service, the program began in 1990 to encourage cities to plant more trees for such benefits as energy savings, air and water quality and higher property values. For the current fiscal year, program officials approved $307,000 in federal money for 20 Florida cities, counties and nonprofits to help support trees.

Under the program, local entities must match the federal grants. And one year after trees are planted, the Florida Forest Service conducts on-site inspections to be sure trees, which are planted on public properties or rights of way, are alive and healthy.

For the study, scientists with UF’s Institute of Food and Agricultural Sciences in 2010 surveyed 2,354 trees planted at 26 sites, including Orlando, Tampa, Ocala, Lakeland and Vero Beach.

They looked at trees planted between 2005 and 2009 to see how many survived and why. Researchers studied trees planted in parks, parking lots, lawns, along streets and in highway medians.

UF researchers say the key is not just planting the trees, but monitoring how long they survive in urban environments.

“Often, folks fall into the trap of measuring urban tree-planting program success simply by the number of trees put in the ground,” said Andrew Koeser, assistant professor of environmental horticulture at UF’s Gulf Coast Research and Education Center in Balm and a study co-author. “They need to become established and hopefully grow long enough to generate all the benefits they are known for.”

The bigger the trees, the more they help society through cooling, increased property values and carbon sequestration, Koeser said.

Scientists studied three species – live oak, bald cypress and Southern magnolia, said Ed Gilman, a UF/IFAS environmental horticulture professor and study co-author.

Researchers counted the number of trees planted versus the number that survived. Trees with at least some foliage were deemed living. They also rated trees on such factors as trunk diameter, crown condition, percentage of crown with live foliage and tree firmness in the ground. The crown includes all parts of a tree above ground.

On-site irrigation that runs on timers played a big role in the trees’ survival and growth, with 97 percent of Southern magnolia surviving on sites with irrigation compared with 74 percent where irrigation was not automatic. Some places didn’t have irrigation on-site, but trees were likely still watered because local entities used a truck with a hose to water them, Gilman said.

As part of the requirements for the grant program, trees found missing or dead within 12 months of planting were replaced. Trees die most frequently during the first two years after planting because of insufficient care, poor nursing stock and vandalism.

Cities throughout America are trying to plant trees. Organizers of a program in South Florida hope to plant 1 million trees by 2020. Similarly, an initiative in Denver aims to plant 1 million trees by 2025, as does New York City.

The study cited only two major cities with tree-survival rates higher than Florida’s urban tree-planting program ─ Philadelphia with 96 percent New York City with 95 percent ─ one to five years after planting.  However, Florida’s program replaces young dead trees, and the study doesn’t account for that when comparing to the major metropolitan areas.

The study was published online in July in the journal Urban Forestry and Urban Greening and will be in the November print edition. Koeser presented the findings in August at the International Arboriculture Society conference in Milwaukee.

Blueberries

Many people around the country, such as the one seen here, are planting trees in urban areas.