Oakland Star-Tulip Booms on Mt. Tam After Prescribed Burn

By Science Communication Specialist Michela Gentile, Golden Gate National Parks Conservancy

This spring, the One Tam Conservation Management Team resurveyed patches of Oakland star-tulips near Muir Woods to see how they responded to a prescribed burn last fall.

One Tam / David Greenberger

July 2025 - It couldn't have been a more perfect spring Mt. Tamalpais morning—wildflowers peeking above dew-covered grass, sun slowly warming the freshest smelling air. We had come to count the points of palest pink that seemed to be everywhere. There were thousands, in fact.

Oakland star-tulip (Calochortus umbellatus) is a California endemic species of lily that grows mostly in the Bay Area, including Golden Gate National Recreation Area and Muir Woods National Monument. Also called the Oakland mariposa lily, it blooms from March to June in shades of white to pink to lavender. It can be spotted growing both in open areas and under shrubs, and even in serpentine soils. And it's one of the rare species that our One Tam Conservation Management Team monitors.

The team mapped patches of the species occurring in grassy areas around Deer Park Fire Road—in Mt. Tamalpais State Park, just outside of Muir Woods—back in 2019. This year, Conservation Management Program Manager David Greenberger led a resurvey effort. He was curious how the species was responding to a prescribed burn conducted in the area the previous fall, opening it up from encroaching shrubs. The increased exposure to sunlight and reduced competition from shrubs, plus the added nutrients from ash, could contribute to a good year for the star-tulip. Beyond that, chemical cues during and after fire can stimulate the growth of flowering bulbs like those in the Calochortus genus.

It was more than an impression that these grasslands seemed a galaxy's worth of star-tulips. We observed an order of magnitude more individuals at each location, totaling 28,535 across three patches in 2025 compared to 1,080 in 2019.

As we head into summer, One Tam partners are working with fire agencies to plan more prescribed burns for the fall. They’re part of our work to support healthy and diverse landscapes, and to reduce risk of intense wildfire. We look forward to more opportunities to observe how the land responds!

For more information

• Golden Gate National Recreation Area Fire Management

---

See more from the Bay Area Nature & Science Blog