How Downtown Ann Arbor Trees Get Watered

The newly-planted trees at the surface parking lot created in place of the old YMCA building, which was demolished earlier this year, sport green bags at the base of their trunks. Most casual observers might guess the bags are used for watering. In this case, a guess based on a casual observation is … exactly right.

What’s not as easily guessed is that these Treegator® slow release watering bags hold 20 gallons of water, take five to nine hours to empty through the 2 water release points, and fit trees from 1 to 4 inches in caliper. A tree’s ‘caliper’ is a forestry geek’s way of talking about the diameter of a tree’s trunk six inches above the ground. Trees up to eight inches in caliper can be watered with the Treegator® system by zipping two bags back-to-back.

The manufacturer’s recommendation is for a fill schedule of once per week, but advises that the watering schedule should be adjusted as needed. In the case of these trees along William St., the guy with the hose [not pictured] said that the schedule had been adjusted to once per day.

Could that schedule be reduced in frequency by coming up with an ingenious way to funnel run-off from the new parking lot towards the trees? Not if the lot has been paved using pervious asphalt–as has been reported elsewhere but not (yet) empirically confirmed by The Chronicle.