Tahoe Yellow Cress (TYC, Rorippa subumbellata) is a small native plant that grows on the shoreline of Lake Tahoe and no where else in the world. It lives only on the sandy beaches and dunes at the ever-changing margin of the lake. Impacts from recreation and development first led to conservation concerns in the 1970’s and TYC has been listed as endangered in both states since 1982. In 1999, a multi-agency and private interest group task force was formed to develop and implement a conservation strategy to promote the recovery and conservation of TYC. The conservation strategy provides an adaptive management framework and options for avoiding, minimizing, and mitigating impacts to TYC and its habitat on public and private lands. The TYC Stewardship Program recognizes the critical role of private landowners in ensuring the long-term survival of TYC.
A similar species can be found growing alongside TYC on the shores of Lake Tahoe. TYC has plump round fruits, fleshy leaves, and a compact growth form, while western cress (Rorippa curvisiliqua) is often taller, the fruits are elongated and narrow, and the leaves are less fleshy and turn purple with age. In contrast to the rarity of TYC, western cress is very widespread throughout the western U.S.
Knowledge of TYC distribution has been developed through shorezone surveys since 1979. Before 2000, surveys followed a general protocol and were completed at various times during the summer. Since 2001, surveys are conducted the first week of September following a standardized protocol. During the first survey in 1979, 32 TYC sites were surveyed; this has since grown to 55 sites. A survey “site” is defined as a stretch of public beach, adjacent private parcels, or adjacent parcels under a combination of private and public ownership. Surveys include stem count estimates as a measure of TYC abundance because clonal growth makes it impossible to distinguish individuals. The amount of available shorezone habitat for TYC fluctuates widely with changes in lake level, with high lake levels leaving little habitat. On average, over 70% of surveyed sites are occupied when the lake is below 6,225 ft. in September, but less than 40% are occupied when the lake level is above 6,228 ft.
To download all of the Tahoe yellow cress data on this page please see Tahoe Open Data.
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