By Will Spangler
There is a small world out there of hard to find rarities that few people even know exist. No, we’re not referring to dedicated botanists, we’re speaking of many listed California native plant species that are the targets of the California Native Plant Society’s rare plant treasure hunts. These treasure hunts are a citizen science initiative started by CNPS in 2010 that take place all around the state “with the goal of getting up-to-date information on many of our state’s rare plants, while engaging chapter members and other volunteers in rare plant conservation.” Often these unique and rare plants are found only in narrow patches of remaining habitat, and it’s important to survey their current distribution in order to best protect them. Historical populations do not always survive, and new patches of plants may spread, so getting out and finding them provides a fun opportunity to put an eye to the landscape and gather information that biologists and land managers can use going forward.
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, with many river miles to paddle and document, is a natural partner to conduct surveys along the state’s waterways, and recently joined forces with CNPS for a treasure hunt around Frank’s Tract where the San Joaquin River braids through the California Delta. With forecasted temperatures for over 100 degrees, the group met at the fine launch site of the Andrea’s Cove Yacht Club to be led by Danny Slakey from the rare plant treasure hunt headquarters. With two sleek double sea kayaks and three single cruiser kayaks, seven plant enthusiasts paddled past invasive water hyacinth and abandoned boats on the way to historical rare plant sites. We first came across an eelgrass that resembled Potamogeton zosteriformis, and then found a rare pea (Lathyrus jepsonii) growing improbably along a modified shoreline atop riprap and many weeds. 
Once we paddled across the main shipping channel between passages of Stockton-bound grain freighters, we came upon beautiful stands of tule reeds (Scirpus acutus), unfortunately interspersed with spreading 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 less rare mints and morning glories. These two small plants, pictured below, are excellent examples of hard to find rare species that are vulnerable to displacement by weeds and dredging, and are very hard to visit via any other method than kayaking right up to them.
After some exhausting morning searching and paddling, we were forced to boat up into some sheltered rushes for lunch, as the levied and fortified passageways of the Delta do not allow for many beaches or anchor points. 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 notes and photographs and charted an easy to find site for future surveys. It’s funny 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 rare native hibiscus with heart shaped leaves (Hibiscus lasiocarpos var. occidentalis), the last rare plant occurrence we would log for the day. After a celebratory rest, we paddled home over glassy water bright with the reflection of the afternoon sun. 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. 
