What is the return on investment for community trees? According to Wikipedia, a return on investment (ROI) is the benefit to an investor resulting from an investment of some resource. A more familiar way to state the question might be, ‘are we getting the best bang for our buck’ in terms of our investment in our community forests? Is the investment in trees worth the money and resources being spent to grow and maintain the community forest?

street trees
Healthy trees are worth the investment. Photo by Guy Kramer.

We know healthy trees provide a plethora of benefits, but the key to gaining those benefits is healthy trees. That takes an investment in time and resources. From planning, to planting, through long-term care, trees in our communities need help to become established. It is only then that they provide the benefits we expect from them. It takes an investment to assure we are receiving a return on investment. Research shows that for every $1 spent on tree care and maintenance, communities receive back over $2 in economic, social, and environmental benefits.

During the Pacific Northwest summer, July through September when we receive little to no moisture, it is particularly important to invest resources to water trees. Best practices for tree care considers the post planting tree establishment period to be two to three years. Most root growth occurs during the summer. Establishment means that many roots will have grown a distance equal to approximately 3 times the distance from the trunk to the branch tips (Gilman 1988;Watson and Himelick 1982).  When trees are provided sufficient water, they establish more quickly. With minimal or insufficient irrigation, or in dryer climates, roots grow more slowly and a tree takes longer to establish.

Past the establishment period, a tree may not need supplemental irrigation, but for recently planted trees, and for those that are being weaned off supplemental water, it is important to watch tree ‘body-language.’ If trees exhibit fall colors in July or August, if the margins of leaves are browning, if leaves look wilted, it is an indication that additional water is required.

Protect your investment. Establish, care for, and maintain trees, then watch the benefits and your return on investment grow.

By Linden J. Lampman, program manager, DNR Urban and Community Forestry Program