This time last year, the city was planning to cut down more than 100 trees due to an emerald ash borer infestation. Luckily, those trees haven’t come down yet—and in fact, beginning this May and June, Somerville will plant 70 trees throughout the city and implement a new watering system that uses drip irrigation bags.
The initiative has been spearheaded by Dr. Vanessa Boukili, the city’s new urban forestry and landscape planner and conservation agent. Boukili, a trained plant ecologist, has been working with the The Mayor’s Office of Strategic Planning and Community Development for the past five months. The goal of the urban forest program, Boukili says, is to “try to think big picture about how to take care of all these trees and make sure we have the best urban forest that we can get.” She helps the city decide when and where to plant trees and assists the Department of Public Works in determining tree maintenance protocols.
Boukili is also behind the decision to change the tree maintenance and irrigation system in the city, moving away from underground tubes used for watering and aerating the soil to drip irrigation bags or “gator bags.” These bags, which are usually green, are attached to the trunk of the tree and have several benefits over the current underground system. According to Dr. Boukili, these bags “usually hold 15 to 25 gallons of water at a time and slowly drip the water into the soil over a number of hours.”
Unlike the underground tubes, the bags make it easier to ensure that the tree is actually getting watered. Moreover, the current underground tubes run the risk of getting filled with sediment, a problem that does not occur with the drip irrigation bags. She also notes that the bags can be removed “once the tree is sufficiently large, whereas the water or aeration tubes remain in the soil for the life of the tree, and can potentially inhibit root growth.”
She says that the city will be careful to plant the right trees in the right place. “Where there are power lines above, we will plant species that are small- to medium-size when they are fully grown so that they do not interact with them,” Boukili says. This includes cherry and crabapple trees, among others. “In areas where we can plant bigger trees that grow to taller heights and provide a lot more benefits to the community and to the climate, we will plant elm, zelkova, pin oak, American hornbeam and London planetree.”
Contractors will fill up the bags twice a week for 30 days after the trees are planted and, after this period, the trees will be watered once a week throughout the summer. They will be responsible for maintaining the trees for two years. Within this period, a warranty will be in place so that trees that die will be replaced by the contractor. The city will keep track of any trees that are not healthy and request replanting if necessary.
The gator bags will let residents know that the tree they’re looking at is a new one, which is intentional, as with the new system, the city will increasingly encourage residents to water both the just-planted trees and any other trees outside their homes or businesses, especially if there’s another drought.
Boukili notes that resident participation is important because it’s hard for the city to water the trees as often as they would like. Last year, Massachusetts went through a historic drought that still affects parts of the state to this day. Dr. Boukili suspects the drought has affected the trees in Somerville as well, and noticed that some “were water-stressed late in the fall.” Some turned brown or lost their leaves earlier than usual, and younger trees are more vulnerable because they don’t have a root system that’s as well-established as older trees, she explains.
Residents can help the city maintain tree health in different ways. They can fill out the tree-watering bags once a week, for example; Boukili explains that the bags don’t hold water constantly, and it can take just four to 12 hours for water to leak out entirely.
“Just because they are empty does not mean they are not working,” she says. Filling these bags is important especially during warm weather and drought periods.
What about older trees or trees that don’t have watering bags? “Residents can water them by hand or use the drip on the hose for 15 to 20 minutes to make sure that they are deeply watering the trees,” Boukili says.
Other practices for general health include putting mulch around the trees. Although the city tries to maintain mulch, residents can help by adding a two to three-inch layer on tree wells that do not already have mulch. Mulch is important because it helps retain water in the soil.
“The important thing is to make sure that the mulch is not touching the trunk of the tree because it can burn the trunk and cause rot of the trunk.” She advises to“mulch, but mulch carefully,” and asks residents not place mulch within two to three inches of the trunk.
And if you notice that a tree looks unhealthy, you can always contact 311 to note those concerns, requesting that the city maintain the tree pit or trim dead branches.