The Point Isabel shoreline is an interesting place. Volunteers have turned the section of this East Bay Regional Park that borders a tidal marsh on its east side into a native garden showcasing a variety of hardy plants and trees. As a volunteer, I was paired with Tom and Jane Kelly, the leaders of revegetation projects here. They tasked me with being the steward of a small section of the park. This meant being available to plant, weed, and water as needed, tasks I generally love.
The revegetated area of Point Isabel Regional Shoreline runs along Rydin Road in Richmond and is basically a landfill full of concrete, various hard materials, and dirt. Yet through the efforts of volunteers, it is now rich in diverse herbs, grasses, and shrubs. Tree cover is a bit sporadic: young coast live oaks and buckeyes are fairly abundant, and there are a few native black cottonwoods (Populus trichocarpa) scattered around the site. Once mature, these cottonwoods will be the tallest trees in the landscape: they can grow to 100 feet tall in their native habitats. With their nice upright form and shimmering green leaves, they create a lush feel, a look I really like. Tom, Jane, and other volunteers previously planted three healthy cottonwoods, spread apart along the east-facing bank. Though they were healthy, they were separated from each other in a slightly artificial way. It looked to me like they yearned for companions, and Tom and Jane agreed. They happily approved of my plan to add more and create a natural “grove.”
So in late February I sought them out. I had made the treks to local native nurseries before and always had a great time looking at the plants and possibilities. I had mostly gone to Point Richmond’s Watershed Nursery in the past, when I got plants to restore a section of lower Codornices Creek. They supplied me with alder (Alnus sp.) and bigleaf maple (Acer macrophyllum) but didn’t have black cottonwood. This time was no different. In fact, for whatever reason, none of the native nurseries on either side of the Bay had any black cottonwood babies. What they did have was Fremont cottonwoods (Populus fremontii), best suited to warmer inland places. Due to climate conditions and the need to match the ones already there, I knew I needed black cottonwoods for Point Isabel.
If I was going to get any in the ground before it got too dry, I needed another plan, so here’s what I decided to do. I remembered that the willows planted along Codornices Creek started as stick cuttings that were stuck into the muddy banks. In that environment they grew fast and tall and created the main bulk of the forest that now lines the creek. I hoped that black cottonwoods, in the same family as willows (Salicaceae), might do the same. I did a quick search on the internet and found that they grow well from cuttings, just like willows. Various websites also had recipes for success with the cuttings, including how long and thick they should be, and how much to leave above and below the soil line. The sites differed a little in their recipes, so I combined the information and came up with my own hybrid one. Hoping for the best, I went to work.
Of course I needed a source for the cuttings: mature trees with branches that were easy to reach and cut. My other restoration project, on Codornices Creek, had some, including one I had planted that was now twenty feet tall. I cut a total of six branches from five different trees with diameters between one-half and three-quarters of an inch. The guidelines I had seen online generally agreed on this as a recipe for success. Each should also be about four feet long and planted into moist ground with half the length above the ground.
I kept them fresh by wrapping them in wet paper towels and immediately brought them to Point Isabel. Since it was the last week of February in a dry year, I wasn’t sure if there would be wet, suitable places to stick the cuttings. So, armed with a piece of metal rebar, I arrived at Point Isabel and began to poke holes. It took about an hour of exploration, but I managed to find six spots with damp ground for the cuttings.
I did my best to shove each cutting into the narrow holes I made so they were halfway submerged. Hard ground made the job difficult, but I came close enough to feel confident about their future success. Two were on the bank near established black cottonwoods, and four were on the far eastern edge of “my” section, close to the marsh. It was nice to make a mini stand there to enhance its future look and to replace one dead small cottonwood nearby that appeared to have baked in the drought. I watered and fed the cuttings, added some mulch around the base of each to retain moisture, and let nature literally take its course.
Now it was a matter of time. I checked for signs of growth each week and saw nothing for the first three. But finally, on March 24, I could see results. Five of the cuttings were showing a few tiny red dots (buds) in various places, and one already seemed to be growing tiny leaves. It worked!
With newfound hope, I continued to feed and water them every week. After another month, they were turning into saplings, and the cutting that got off to a slow start was now sprouting too. I had expected that not all would be total successes, which is the reason I got a half dozen to begin with. Sure enough, by late April one was struggling. It was the skinny runt of the litter, with the smallest diameter. Perhaps because it was too thin to begin with, it soon showed little sign of life. By mid-May it appeared to be history, and I cut off its life support. Now only the thriving five would get the food and water with their weekly visit. But as of mid-June, the fab five are all doing great, even though they all look somewhat different from each other.
I have a theory about why they differ in their look, even in youth. It’s because they’re not exactly the same tree. During my research into black cottonwoods, I read that they hybridize easily with Fremont cottonwoods, especially in areas where their habitats overlap, like the Bay Area. The cottonwoods planted along Codornices Creek during the initial restoration phase are almost certainly hybrids, but the three trees previously planted on the bank at Point Isabel are black cottonwoods, as is the tall one I planted at Codornices Creek. At a glance, they look very similar, but the leaves of the hybrids look a little bit like Fremont cottonwood leaves, with small serrations along the edges. True Fremonts have noticeably serrated, heart-shaped leaves, while black cottonwoods are nearly smooth and more oval. (See the photos for reference.)
My cottonwood babies at Point Isabel are all hybrids except the cutting taken from a pure black cottonwood. That being said, I’m sure they’ll find harmony as they grow together, and almost no one will notice. Instead, visitors will experience the joy of a small piece of wild land on the mend, a bit of nature triumphant in an increasingly artificial world.
As luck would have it, there arrived another new addition to the cottonwood grove at Point Isabel, this time more of a teenager than a baby. During my search for black cottonwood seedlings in February, I stopped in at little Oaktown Nursery in West Berkeley and discovered they only had numerous Fremont cottonwood seedlings, which I didn’t want. But about three weeks later, Tom and Jane had some interesting news for me. Kristen Hopper from Oaktown Nursery remembered me coming in. She had been talking to Jay Cassianni from the Friends of Sausal Creek Native Plant Nursery, who had a black cottonwood needing a home. It had been there for some time and was already tall and treelike. All I had to do was pick it up.
And so, on March 27, we welcomed the newest and most mature addition to the Cottonwood family. About seven feet tall, skinny, and rootbound, the gawky but sturdy teenager was finally getting a change of address. We dug a deep hole, filled it with nourishing potting soil, and watered it well. This foster child now had its forever home. And although it took several weeks to adjust, today it has new growth to show its gratitude.
So, with a total of six additional cottonwoods, Point Isabel has a chance to become a paradise as its new tall green border takes hold along the edge of the marsh. With the help of these trees, Point Isabel will look more like a native Garden of Eden than the neglected landfill it once was.
— Randal DeLuchi, Point Isabel revegetation volunteer who also worked with the West Contra Costa School Garden Program for ten years, using gardens in education.