Summer at the CLLA (Meek)

Most of July 2024 has seen Portland seared by an unrelenting heat wave. Although temperatures are not as high as they were in the record-breaking June 2021 three-day heat dome, the day-after-day string of 90-plus days with no rain has been hard on trees all over the city. But that has not been the case with the trees at the Concordia Learning Landscape Arboretum (CLLA) at the former Meek School, thanks to dedicated volunteers with the Concordia Tree Team who have been diligently watering trees every week.

At least six trees at Meek were planted only this spring and still have very small root zones. These include a cork oak, Chinese ironwood, Chilean beech, Japanese raisintree, silver linden and a Henry linden. Those young trees are only able to draw water from the volume of soil their roots have spread to. By watering deeply, these young trees are encouraged to spread their roots downward into the moist soil. By having easy access to water, these trees are able to continue making food for themselves through photosynthesis, a process that requires water.

Compared to unwatered trees in the rest of the city, those at the CLLA have grown much faster. Several of the original trees planted in 2010 are now 20’ tall or higher. The tallest appears to be the arboretum’s dawn redwood. Where there previously had been no shade at all, visitors and their dogs now can sit or stand in enlarging pools of shade cast by the rapidly maturing trees of the arboretum.

For now, those pools of shade are not far from the trees making them. But within a few more years, some of the largest oaks will have spread wide enough and grown tall enough to create almost a continuous umbrella of shade to protect human and canine visitors from the hot sun. And the trees don’t just cool the air by shading it. By releasing water vapor during photosynthesis, they also cool the air when that water evaporates. So in time, the arboretum will serve as a cool-air reservoir for the neighborhood.