Planting trees is an effective tool to fight the “heat island” of the city

By TRUDY DUNHAM

There is an old Chinese proverb: “The best time to plant a tree was 20 years ago. The second best time is now.” In this period of rapid climate change, the proverb is certainly true. We need trees today more than ever.

Why? It is getting hotter in St. Paul.

Photo left: Members of the Hamline Midway Progressive Women’s Network look on as City of St. Paul Urban Forester Zach Jorgensen plants one of the trees they donated to Hamline Park.

Climate change means that St. Paul is experiencing the urban “heat island” effect. Built-up areas (areas with more buildings and pavements) are hotter than forested areas. Pavement and roofs absorb more sunlight and then radiate the heat back into the neighborhood. We can expect St. Paul daytime temperatures to be higher than local rural areas, and our summer nighttime temperatures may be much higher. Trees can moderate this effect. Trees better reflect the sun’s rays than do pavement, provide shade and the evapotranspiration process cools as it releases moisture into the air. Well-shaded neighborhoods can be significantly cooler in the summer.

Climate change also results in more “bad air days” when those with respiratory problems find it difficult to breathe outdoors. Health warnings will encourage you to stay inside and keep your windows closed. The higher temperatures, more stagnant air, and higher humidity result in higher ozone levels and air pollution. Trees help to filter the pollutants and absorb carbon dioxide, making the air cleaner and healthier for you to be outside in your yard, walking or jogging.

The City is already at work adding to our urban tree canopy. Zach Jorgensen, Urban Forester for the City of St. Paul, says “The Hamline Midway neighborhood is on this year’s planting list,” so expect to see new boulevard trees. They will replace trees lost to heat stress, the emerald ash borer, and other causes.

What can we do as residents to support the urban tree canopy in our neighborhood? Ready and Resilient recommends several actions:

1) Keep the trees we have healthy by watering the trees in your yard and along the boulevard when rain is scarce. One of the side effects of climate change is severe weather: periods of heavy rains interspersed with long periods of no rain. Trees become stressed without adequate water. When you notice that your lawn or garden needs watering, don’t forget to consider your trees. Newly planted trees are especially susceptible and require frequent watering if there is no rain. Established trees prefer less frequent but longer soakings, enough to moisten the soil all along the tree drip line to a depth of 10-12 inches. Check the St. Paul Forestry website (https://www.stpaul.gov/departments/parks-recreation/natural-resources/forestry/tree-maintenance) for recommendations.

2) Donate a tree to the St. Paul Parks. Your support for parks can speed up the City’s timeline for tree planting. The easiest way to do this is through the Friends of the Parks and Trails (http://friendsoftheparks.org/) annual spring tree sale. Check that you want to donate the tree to a local park. Write in the park to which you want to donate (don’t list Newell or Como: they don’t need additional trees), or just say “a park in the XYZ neighborhood” (whatever neighborhood you choose). The order deadline is Apr. 22. The City plants the tree for you. Can’t afford to donate a tree? Talk to your neighbors. Last year members of the Hamline Midway Progressive Women’s Network pooled their resources and together were able to purchase three trees for Hamline Park.

3) Plant a tree in your yard. If you own your home or your landlord okays adding a tree to the yard, consider whether your yard can support a tree. You will need a large open space away from buildings or other structures, open to the sky, with no power lines above you or buried utilities below you. (Note: It is state law that you contact Gopher State One Call, 651-454-8388, before you dig!) The space needed will vary with the tree you choose. Consider the tree’s canopy or drip line: the diameter of the tree plus the length of its branches in each direction at maturity. For a mature shade tree, this can be 20 to 40 feet, and its roots will be at least that wide. A healthy tree requires this much space to grow. Check with experts to decide what to plant: our average temperatures will be 4-5° F higher by mid-century, and trees that currently flourish 200-400 miles south may be your best options. If you need help deciding whether your lawn can support a tree or what type of tree to plant, contact the Ramsey County Master Gardeners (call 651-704-2071 and leave a message; a MG will return your call). The Friends of the Parks and Trails (http://friendsoftheparks.org/) tree sale offers trees in a variety of sizes appropriate to our area.

4) Plant a tree on a public boulevard. After 2016, the next time the City is scheduled to plant trees on Hamline Midway boulevards is 2021. “Residents are welcome to plant trees on public boulevards,” Jorgensen said, “though we do require an approved no-fee permit available through the St. Paul Forestry office to do so. We will review the site and the proposed tree type to make sure the site is suitable for tree planting and the tree type is appropriate for the location.” You are responsible for planting the tree. Check the details at https://www.stpaul.gov/departments/parks-recreation/natural-resources/forestry/tree-permit-terms-and-conditions.

Support our neighborhood tree canopy. Water your trees. If you can, donate or plant a tree this year to keep our neighborhood cool and healthy!

The Ready & Resilient Hamline Midway project is an initiative of the Hamline Midway Environmental Group (HMEG) to build climate change resiliency in our community.