They say that cats have nine lives. How many lives can a wetland have? The Princeton High School Ecolab Wetland is now beginning its third. Lush and verdant in June, it was stripped bare of vegetation for the second time in its 17 year history at the beginning of July. The first time this radical change happened, in the fall of 2022, took me and environmental teaching staff completely by surprise. This time, the lines of communication were open, and the reasoning fully understood.
On June 12th, the wetland--a brick-lined detention basin squeezed between the science and performing arts wings of the school on Walnut Street--looked like this. The elderberries were abloomin' along the edges of lush sweeps of sedges, rushes, and wildflowers that thrive in full sun and ground magically kept moist by sump pump water.
There were also cattails, lots of cattails--narrowleaf and broadleaf. Cattails, with their vertical hotdog-shaped stalks raised high, are the iconic wetland plant. But when I see cattails in a wetland that I'm taking care of, my reaction is "oh, oh." You may see cattails being overwhelmed by the tall invasive reed Phragmitis in the ditches along freeways, but in a sunny wetland like the high school Ecolab, cattails themselves can play the bully, spreading aggressively with the thick rhizomes they send out in all directions.
Thus, when I stopped by the Ecolab less than a month later, on July 7, and saw all that lush, beautiful native vegetation stripped bare, I grieved the loss, but I also saw a potential silver lining.
The reason for the transformation was the need to replace two of the basin's walls. The blocks originally used to make the wall had become corroded by salt used to de-ice the adjacent walkways in winter. Replacing the blocks required complete demolition and rebuilding. The large tubes in the photo conveyed the frequent discharges of sump pump water away from the work area.
During the repair phase, I was in ongoing communication with the contractor, Patrick, and environmental science teacher Jim Smirk. I wanted to make sure that the hydraulic conditions so favorable to diverse wetland plant growth--the combination of some higher ground with a series of three pools to transport the sump pump water slowly towards the drain--would be restored. Though I was out of town on a band tour in Michigan, Patrick was very accommodating and even sent a photo to make sure he had reformed the ground the way we wanted.
It may look like a moonscape, but already some of the old vegetation is beginning to reemerge from whatever roots are still intact. We may need to do some replanting, but after 17 years, the soil should be packed with native seed ready to sprout over the coming year.
Now is a critical time for the Ecolab's future. That first stripping of vegetation in fall 2022 had been prompted by willow trees that had grown too big for the site. As vegetation rebounded, I assiduously removed the sprouts of willows and any other trees with the potential to grow too large. This time, it's the cattails that pose a danger.
What plant species are going to feed off of all that wonderful sun and cool sump pump water from the high school's basement? If we let the cattails reestablish, the Ecolab will eventually become stuffed with cattails and little else. If instead we remove all sprouting cattails and encourage native species that are less aggressive, then it will be much easier to sustain biodiversity over time. As with the growth and development of people, intervention early on in a wetland's rebirth can determine longterm fate.
Related posts:
A Wet Meadow is Born -- We used a similar strategy of early and ongoing intervention when a detention basin was replanted with native species in Princeton's Smoyer Park 9 years ago. That wet meadow is now thriving, with very few weeds and lots of native diversity.
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