Not all updates bring good news. In February of 2021, I planted black cottonwood cuttings (Populus trichocarpa) near the marsh at Point Isabel, hoping all would thrive in this windy bayside location. Others had been planted by volunteers a few years ago and had grown into 15-foot trees, even after years of drought. My five cottonwood cuttings and one donated sapling were placed between these trees in hopes of creating a natural-looking future grove.
I planted them all closer to the tidal zone than the existing trees, thinking they might benefit from damp soil as long as it wasn’t too salty. On the steep slopes of the levy-like banks, it was easy to see where the tidal zone began. It was marked by a sudden end to the wild grasses and a swift transition to the cordgrass and pickleweed that thrived in the marsh. I planted two cuttings and the donated sapling along this steep bank where the transition was easy to see.
But in one broad open area with a very gentle slope, the transition zone was almost invisible. I judged it the best I could by looking at the change in plant communities here, but I couldn’t find a crisp line of change. Everywhere I looked was a hodgepodge of grasses, mostly looking like they came from a faraway desert. Adding to the mess was a giant, partially buried sewer line that extended from the wetlands across the marsh until it dove under the I-580 freeway.
Near the bike path, this area had been extensively planted with natives of all kinds, but near the shoreline, it was barren. It was in this barren zone that I planted three of the cuttings with the hopes of someday creating a small forest and making a wasteland look natural again. However, my misunderstanding of tidal dynamics would cost two of the cuttings their lives. It would also mean re-thinking my rehabilitation plan.
I had never heard of king tides until about three years ago. To me they were like a new discovery that was now everywhere. In late summer 2021, I went to check on the cuttings and noticed that two had died suddenly despite being alive and healthy just a week before. These two were closer to the edge of the wetlands than the one that was still alive. At the time, I was mystified. What happened out there over the course of the week? Why was the other one okay?
It wasn’t until I heard about the king tide forecast for January 2 of this year that I began to wonder if I planted the cuttings too low. Maybe they had been inundated before by this very same thing. The January event was forecast to be an extra strong one, and I realized this was my opportunity to find out. I had to see if my cuttings might actually be submerged by tide levels I never imagined. The peak of the high tide was forecast for 10:15 am, so I timed my visit accordingly.
Nature put on a great show that day. At its peak on January 2, the water not only covered the tops of the cordgrass in the inlet, but it created an inland sea. And sure enough, the dead cuttings were inundated too, flooded with brackish Bay water an inch and a half deep. The cutting that was a few feet away from the lowest two was above the water line and still alive but barely out of harm’s way. Bay water had soaked two cottonwood cuttings, creating a higher salinity level than the species could tolerate, likely killing them in the process. Although I wasn’t there to see the original killer tide sometime in the summer, here was evidence of a problem, almost certainly the reason the cuttings were dead in the first place.
(Note: I learned some time ago that you can see if a deciduous plant is alive in the winter by scraping a tiny bit of stem bark with your fingernail. If green appears easily under the bark, it’s alive. If it’s brown or gray, it’s gone. This is how I knew who was alive and dead out there.)
Frustrated at losing part of my future forest, I decided to add a few different saplings higher up in the same area. For just five bucks each, I got three baby California sycamores (Platanus racemosa) from The Watershed Nursery and stuck them in a bare area upslope from the cottonwoods. Normally these trees enjoy a creekside home away from the Bay. However, I noticed that the East Bay Regional Park District had already planted some that were doing well in McLaughlin Eastshore State Park in essentially the same environment as Point Isabel. There are no guarantees, but I thought I could use their example. If they could make it work, so could I.
Barring tsunamis and other extreme factors, the new trees should at least get a successful start. If they do well, they will not only grow into stately trees, but also provide habitat for a number of critters that would enjoy making the park their home. And with it all, a lesson learned. Know your habitat well—really well—when you are planting natives. On this changing planet, it’s only going to get harder.
— Randal DeLuchi is a Point Isabel revegetation volunteer and described planting his cottonwoods in “Little Cuttings That Cut It” for the July 2021 Bay Leaf.
February 2022
