California’s Hidden Vernal Pools Are Blooming Right Now and Most People Have Never Seen One

Scattered across the grasslands of Northern California, small seasonal pools are quietly putting on one of the most remarkable natural shows in the state. Most people drive right past them without knowing they exist.

They are called vernal pools, and the California Department of Water Resources recently highlighted them as one of the state’s most ecologically significant and least understood landscapes. These shallow depressions form in grasslands with an impervious layer of rock or clay beneath the surface that traps winter rainwater. The pools fill during the wet season, bloom with life in the spring and dry out completely by summer.

What makes them special is what lives inside. Vernal pools support an extraordinary diversity of plants and animals, many of which are found nowhere else on earth. Fairy shrimp, tadpole shrimp and other invertebrates hatch from eggs that can lie dormant in the soil for years, waiting for the right conditions. Rare wildflowers ring the edges of the pools in concentric bands as the water recedes, creating colorful bullseye patterns visible from above.

Despite their ecological importance, vernal pools have been dramatically reduced across California. Urban development, agriculture and changes in land use have eliminated the majority of the state’s original vernal pool habitat, making the remaining pools especially valuable for conservation.

You can find vernal pools in grasslands around Butte, Sacramento, Placer and Yolo counties, among other areas. Spring is the only time to see them at their best, and this year’s late rains have helped extend the bloom into late April and early May.