Plants with less-than-showy flowers tend to get overlooked, even by some of the sharpest botanists. When a plant is only a few centimeters tall and flowers later in the season than its more eye-catching neighbors, it can be even easier to miss. The Scotts Valley polygonum (Polygonum hickmanii) is a case in point. This tiny species was first described in 1995 and was already very rare. It occurs in a limited urban area in Scotts Valley, near Santa Cruz, California, where it is under pressure from development. Only 2,100 plants were observed in 1997, and in 2003, the United States Fish and Wildlife Service listed it as endangered under the federal Endangered Species Act.
As the curator of the University of California Botanical Garden at Berkeley, I work with the national Center for Plant Conservation and a coalition called California Plant Rescue. Each year we make an ambitious plan for conservation fieldwork in the greater San Francisco Bay Area, and for 2020, we planned a packed calendar. Most of our fieldwork was derailed by the restrictions put in place to limit the spread of COVID-19, especially given the timing of the restrictions. Annuals and herbaceous perennials on California’s Central Coast tend to have a short spring cycle of growth and seed set. By the time permission was given to be in the field for just day trips, seeds had already set and been dispersed for many species.
Scotts Valley polygonum, in contrast, is an annual wildflower that typically starts to germinate in December, flower from May to August, and set seeds in August. The species is now known to occur on less than an acre of private land adjacent to a new housing development. The development company established a conservation easement to protect Scotts Valley polygonum and another endangered species, Scotts Valley spineflower (Chorizanthe robusta var. hartwegii). Both species are in the buckwheat family (Polygonaceae). In 2015, no Scotts Valley polygonum were found at this site, and it wasn’t until 2020 that the number of plants went above four hundred, less than 25 percent of the population observed in 1997.
In the past, Scotts Valley polygonum has been documented at two nearby locations, but no specimens have been observed there in recent years. One of these locations is a special ecological preserve adjacent to Scotts Valley High School, where the polygonum has not been observed since 2015. The site is fenced and managed to support the species, but we have limited hope it will reappear on its own.
When my colleagues and I could finally return to the field, pandemic protocols required all participants to travel solo in vehicles and to maintain at least a six-foot distance from one another when working at the sites. I was fortunate to work with two other botanists, Kathy Lyons and Jaymee Marty, at the easement site on August 7. We declared ourselves free of COVID-19 symptoms and signed liability waivers for the landowner. The plants occupied an area of less than forty square feet, scattered across an undulating grassland. We worked for hours on hands and knees making a modest seed collection from the less than five hundred plants—all that is left in the world.
As we collected the tiny seeds from the plants (removing only a small percentage of the seed set), we remarked on how it almost felt normal to be in the field again, despite the pandemic. Travel restrictions had resulted in a huge reduction in the number of cars on the road, which meant that, as a side benefit, travel between Berkeley and Scotts Valley flowed along at the speed limit, instead of crawling through typical Silicon Valley gridlock. Travel each way took one hour instead of the usual three.
A few weeks after our work, the CZU Lightning Complex wildfire in Santa Cruz and San Mateo Counties blackened over eighty-six thousand acres, starting on August 16 and continuing through September 22. The evacuation zone included the two historic polygonum sites. The only extant site, from which the seeds had been collected, was on the margin of the evacuation zone, just across a four-lane highway. It could have easily been different. The fire burned so hot in places that any seeds present in the soil were cooked. During the fire we anxiously checked the maps. It was a great relief to learn that the polygonum sites did not burn.
Our purpose for collecting seeds was twofold: first, to create a conservation seed bank as a backup in case the population is lost for any reason, and second, to produce more seeds by growing plants in a nursery environment. This amplification of seed numbers may make it possible both to reestablish the plants at their historic sites and to augment the numbers of plants within the conservation easement.
In November, propagator Susan Malisch at the University of California Botanical Garden sowed one-third of the polygonum seeds from our seedbank. As of late January 2021, over 85 percent germination has been observed. Each seed was sown individually to minimize root disturbance when the plants are moved into larger containers. The plants aren’t likely to grow larger than six inches tall and perhaps two inches across—giants compared to the plants in habitat, where they are crowded together and typically grow about one and a half inches tall.
We look forward to a successful crop of Scotts Valley polygonum in 2021. If all goes as planned, we will have thousands of seeds to use in saving this species from extinction. Wildfires and other threats still pose an incredible risk to the species, but with a robust conservation seedbank and the knowledge of how to grow the plants to reproductive size, we can safeguard its future. Botanists are paying close attention, and Scotts Valley polygonum is no longer overlooked. Next November, we plan to work with the federal Recovery Implementation Team—a team established by the Fish and Wildlife Service—to place seeds back into the habitat.
Holly Forbes is the curator of the University of California Botanical Garden at Berkeley. Support for the Scotts Valley polygonum project is provided by the Ventura Office of the United States Fish and Wildlife Service.
Citation: Forbes, H. 2021. A Conservation SOS: Polygonum hickmanii. Arnoldia, 78(3): 5–6.