Peter Foster

Peter Foster, chair of the Marine Forest Advisory Commitee, waters a tree in the Marine Elementary School playground. 

Soon after moving to Marine on St. Croix in 2019, Peter Foster joined the Forest Advisory Committee and became the adoptive father of a dozen public trees. 

Now you’ll find him checking the sprinkler in the gravel bed by the Marine Elementary School where dozens of little tamarack seedlings are growing out their roots in preparation for transplant into the wetland along Highway 95 next year. 

 And once a week, Foster gets out his electric bike, hooks up a cart, and hauls 5-gallon buckets of water from his home to each of the young trees planted on city property in the past two years. Each Treegator® bag he fills helps these vulnerable young trees stay alive through the heat and drought of this summer. 

The Marine Forest Committee grows and distributes trees at no cost to area residents, as well as providing trees for city properties. 

“If you received one of the free trees from the Forest Committee, we hope you will water it each week,” Foster said. “Especially this year, they won’t make it without your help.”

When temperatures rise into the 90s, trees, like people, “sweat.” It’s a process called evapotranspiration that brings water up through the tree’s roots and trunk, and eventually out through the leaves. 

When the ground is very dry, trees struggle to take in water and nutrients. The gas exchange holes in the leaves (stomata) that allow water out in order to retain moisture. If drought conditions worsen, trees begin to drop their leaves. All of this limits their ability to grow and provide much-needed shade for homes, yards and parks.

Trees less than 3 years old are particularly susceptible to heat stress because their root system is not yet well developed. For brand new trees, give them a sip daily. For trees planted 3 to 12 weeks ago, water every 2-3 days. After that, water weekly until the tree is well established.

When temperatures are over 90 degrees, and especially if leaves are beginning to wilt, give your young tree 10-15 gallons of water. The Treegator® bag slowly releases 15 gallons of water, but you can also use a sprinkler or a soaker hose to gently let water soak in around the entire root ball.

Learn more about caring for young trees in high heat conditions by visiting the University of Minnesota’s Extension Service:


Green Marine is an occasional series of stories highlighting the actions people in Marine on St. Croix have taken to improve the environment, protect water and pollinators, save energy, and more. 

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