Since 2025 Maine Audubon has collaborated with the municipalities of Portland, Lewiston, Auburn, and Bangor to establish and operate three community tree nurseries. These nurseries grow trees, historically native to Maine, that can be planted as park and street trees.
In Portland and Bangor we have constructed some of the first Missouri Gravel Beds in the state of Maine. Missouri Gravel beds are an innovative solution developed by Professor Chris Starbuck of the University of Missouri. Instead of being grown in pots or the ground, bare root trees are planted in gravel where they are drip irrigated and stored there until they can be planted out into the landscape.
These gravel beds help mitigate many of the problems trees can develop in traditional nursery settings. Bare root trees are less expensive than larger ball and burlap (B&B) trees. There are also a wider variety of species that can be purchased in bare root form, especially native trees. Trees grown in gravel beds have no reduction in above ground growth, but do have increased amounts of fibrous roots. These fibrous roots allow for nutrient and water uptake and make the trees more resilient when planted out on city streets. When B&B trees are harvested and planted in the landscape they can lose large amounts of their fibrous roots, leading to shock and stunted growth. B&B trees are also heavy, hard to transport, and require much larger holes for planting. Trees grown in gravel beds are easy to remove, transport, and create holes for making the planting process less difficult to do with the help of volunteers, which puts less strain on the resources of municipalities.
Missouri Gravel Beds have been adopted by a number of municipalities in the state of Minnesota, which shares some climate and other similarities with Maine, with great success. The University of Minnesota has collected data on what trees they have found thrive in gravel beds and community stories throughout the state about their beds. Other cities and nurseries throughout the country have also started using gravel beds to improve their planting projects. The city of Springfield, Missouri, Casey Trees of Washington DC, and the city of Roanoke, Virginia, are just some examples of municipalities and nonprofits that have started utilizing gravel beds for growing trees to increase urban canopy.
