Every tree has its tag on SLAC campus in Menlo Park – and that translates to almost 5,000

From 150-year-old native oaks to young redwoods, nearly 6,000 trees grace SLAC’s 426-acre campus in Menlo Park.Most of them are labeled with a three-digit number on a one-inch-diameter aluminum disk nailed into their trunk.

These tree tags are an integral part of a comprehensive SLAC’s tree-management program, started about six years ago to more efficiently monitor the health of the site’s trees and to identify potential personnel and property risks that would require pruning or removal.

With so many trees on site, identifying them accurately and assessing their health annually are the essential parts of the program.

Carlos Pereira, SLAC facilities coordinator, is responsible for the spreadsheet that contains records for the 4,945 “substantial” trees that have been tagged and mapped. Young trees with trunks too small to tag, such as newly planted memorial trees and the 400-some oak trees planted this year around the Arrillaga Recreation Center, are also monitored.

The site is divided into seven sectors, each with its own tag-number sequence. For the past three years, Neil Woolner, a certified arborist consultant with the tree management company Arborwell, has performed the annual assessment and given his prioritized list of recommendations.

“We try to be proactive instead of reactive,” Pereira said. For example, a number of ash trees near Building 41 were pruned recently after Woolner’s latest assessment. Unfortunately, it’s not possible to forecast all potential hazards. Pereira said, during a windstorm a few months ago, some sweetgum (Liquidambar) limbs fell and scratched a few cars parked in Lot E, southeast of the Café – prompting a quick pruning of other trees in that area.

Woolner also noticed that a memorial redwood near Building 41 appeared not to be thriving. He recommended adding mulch to reduce heat stress, adjusting the watering and improving the area’s drainage. The tree quickly perked up.

“The single most important thing you can do for any tree is to mulch it as much as you can,” Woolner said. “You’re copying the forest environment. Mulching creates a decaying microclimate beneath the tree in which thriving fungi feed the soil and combat diseases. Pests avoid healthy trees.”

Photo by Mike Ross for SLAC Today