Pennyroyal Eradication

A multi-year project to preserve Hidden Lake's vernal pool.


Maintaining Progress

Due to COVID-19 pandemic restrictions in 2020, the usual large groups of Parks staff and volunteers did not pull pennyroyal at Hidden Lake. But a small Parks team accomplished the annual project goal by putting in several days of hard work over the summer. This ensured no progress was lost in the efforts to reduce invasive pennyroyal and preserve Hidden Lake.



Hidden Lake, a seasonal pond in Mount Burdell Preserve, provides habitat for several varieties of frogs and other amphibian species. Over several years, work crews have hand-pulled invasive plants, predominantly pennyroyal, which threaten to crowd out native vegetation and choke the pond's seasonal waters. Pennyroyal also has properties that, if ingested, are toxic to some mammals

Managing the invasive vegetation at this location by hand-pulling characterizes Marin County Parks' commitment to an organic first approach.

Thanks to these efforts, during rainy season visitors to Mount Burdell continue to enjoy the thunderous singing of the many frogs that gather here to celebrate wet weather.