Town of Vienna’s remaining trees are unusually healthy, inventory finds

Vienna’s tree canopy may be shrinking, but the trees still standing are actually doing quite well, a recently released town-wide inventory found.

About 88% of the 7,224 trees on public land examined by PlanIT Geo are in “fair” or “good” condition, the consultant told the Vienna Town Council when presenting its findings on June 20.

“I’ve looked at a lot of data across a lot of projects, and I don’t think I’ve seen one as good of health as Vienna’s trees are in,” PlanIT Geo Director of Field Operations TJ Wood said, decreeing the town’s tree population to be in “very good health” overall.

That does still leave roughly 722 trees that were found to be in poor condition or dead, according to the inventory, which was initiated based on a recommendation by an urban tree canopy assessment that the town received last October.

Focused on trees on public property, including any within the street right-of-way and parks, the inventory identified tulip poplars as the species with the highest mortality rate at 12 dead trees. The species with the biggest showing in the “poor” category was red maple, which isn’t surprising when it constitutes 16.6% of the total inventory, Wood said.

He reported that, while Vienna has “a very diverse urban forest overall” with 162 unique species, the top 10 most common species make up almost 51% of the population, led by the 1,200 red maples recorded by PlanIT Geo.

“There’s a lot of room to diversify tree plantings and try new species out,” Wood said.

In another sign that Vienna could use some more trees, less than 30% of its trees have a diameter of 1 to 6 inches, suggesting the town is “lacking in new plantings.” Wood added that the town could get close to the ideal rate of 40% if it puts a tree in all 1,222 sites that the inventory identified as suitable for plantings.

Despite the overall healthiness of Vienna’s urban forest, the inventory says 3,968 trees, or 65% are in need of some maintenance. The majority are recommended for some kind of pruning to remove dead wood and hanging limbs or prevent them from growing into utility lines, signs and other infrastructure.

However, 290 trees were deemed to be at moderate risk, meaning they should be revisited at least once a year, and there are 25 high-risk trees.

“I would recommend anyone visit immediately and get another set of eyes on them, decide whether those need to be removed, or if there is a mitigating factor that can be done to reduce that risk to public safety,” Wood said, pointing to a red maple with a split trunk that could fall on a street or sidewalk as an example of a high-risk tree.

Vienna Park Maintenance Superintendent Jeremy Edwards noted that there are still some trees in parks, including Northside and Wildwood, that haven’t been examined and added to the inventory yet. The survey didn’t include trees on private property and along the Washington & Old Dominion Trail, which isn’t town-owned.

All of the data collected is now publicly available through a TreePlotter database that town staff will be able to update in real time.

Last year’s tree canopy assessment found that the town’s canopy has declined by 163 acres, or 13%, since 2011. In January, the town council designated improving the canopy as a top priority for 2023, and Vienna is currently considering an ordinance that would require developers to preserve trees, instead of just replacing ones they cut down.