Rivers for Change Hunts for Treasured Plants

By Will Spangler

Hidden among California’s treasures are a trove of rare plants uniquely adapted to California’s varied geography. These endemic plant species are the targets of the California Native Plant Society’s rare plant treasure hunts, a citizen science initiative of the CNPS designed to gather information on our state’s rare plants and encourage rare plant conservation. Often these special status plants are found only in narrow patches of remaining habitat, and it’s important to survey their current distribution in order to better protect the plants and the wildlife that depend on them.

Photo: Will Spangler

Many rare and threatened plants occur along rivers and riparian corridors, which are dynamic and often shifting places that pose a variety of access challenges. Rivers for Change, a non-profit dedicated to paddling and protecting California’s rivers, is a natural partner to conduct surveys along the state’s waterways, and in June 2012 joined forces with CNPS for a treasure hunt around Frank’s Tract where the San Joaquin River braids through the Delta. Seven plant enthusiasts took to the water in kayaks and paddled past invasive water hyacinth and abandoned boats on the prowl for rare plants. We first came across an eelgrass that resembled Potamogeton zosteriformis, and then found a rare jepson’s pea (Lathyrus jepsonii) growing improbably along a modified shoreline atop riprap and many weeds.

Once we crossed the shipping channel between Stockton-bound grain freighters, we came upon beautiful stands of tule reeds (Scirpus acutus), unfortunately interspersed with invasive Arundo donax, the giant reed that’s choking California waterways. Continuing along, an astute observer in the group noticed exposed mud and roots, and paddling closer, found the tiny and beautiful flowers of mason’s lilaeopsis (Lilaeopsis masonii) and Delta mudwort (Limosella australis/subulata), growing beneath mints and morning glories. These two very small plants, pictured below, are excellent examples of hard to find rare species that are vulnerable to displacement by weeds and dredging, and are difficult to visit without kayaking right up to them.

Delta mudwort Photo: Will Spangler

Upon resuming our hunt, we paddled up to former wooden dock pilings and to our pleasant surprise found the next rare plant of the day, suisun marsh aster (Symphyotrichum lentum), growing right out of the decomposing wood! Surmising that birds may have deposited the seeds here, we took photographs and charted an easy to find site for future surveys. It’s uncanny how these rare plants, usually so hard to uncover, can occasionally find the most obvious spots to hide. After finding the aster, we took the long loop back to our put-in, and it was along Fisherman’s reach, a levied and channelized stretch of Delta, that we found a native hibiscus with heart shaped leaves rose mallow (Hibiscus lasiocarpos var. occidentalis), the last rare plant occurrence we would log for the day. It was a successful day, cataloguing six occurrences and seeing firsthand both how little habitat remains for these rare plants and the encouraging signs of resilient plants making the most of their environment.

Photo: Will Spangler

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