Merced Vernal Pools and Grassland Reserve

Our class made a brief stop on transit to Yosemite so that we could check out the vernal pools near the campus of UC Merced. The entire Central Valley of California used to be a complex of grasslands and wetlands drained by the Sacramento and San Joaquin Rivers. This fertile soil is wonderful for agriculture. Combined with the hot summers and mild winters, pretty much every temperate crop is grown somewhere in the valley. This is great for feeding Americans, but bad for the native flora and fauna, many of which are endangered. The Central Valley habitat with the highest concentration of unusual plants is the vernal pools. These temporary wetlands are formed when depressions in grassland form a clay hardpan under them, causing winter rainfall to collect on the surface. Plants in these habitats have to deal with this hard compacted soil as well as the brief spring growing season. It takes a specialist to deal with being completely submerged after the winter rains and totally desiccated by the long summer dry season. Thus most vernal pool species are fast-growing annuals only found in this habitat.

We managed to hit the ponds at pretty much at peak bloom, but we only had a couple hours to spend there. I had to hurry to find as many plants as I could in the limited time. Here’s me doing some fast-paced botany on the edge of a particularly diverse vernal pool.


I’m just going to throw up the highlights of plants from the day in no particular order. All of these are annuals mostly or exclusively found in vernal pools. Many are close relatives of plants found in Santa Cruz or the Coast Ranges, so they look similar to previous photos on this blog.

Downingia_bicornuta (Doublehorn calicoflower, Campanulaceae)



Plagiobothrys stipitatus (Vernal Pool Popcornflower, Boraginaceae)

Plagiobothrys stipitatus

Brodiaea appendiculata (Appendaged Brodiaea, Themidaceae)

Brodiaea appendiculata

Sidalcea hirsuta (Hairy checkerbloom, Malvaceae)



Pogogyne zizyphoroides (Sacramento mesamint, Lamiaceae)



Eryngium castrense (Great valley button celery, Apiaceae)



Mimulus tricolor (Tricolored Mimulus, Phrymaceae)



One thought on “Merced Vernal Pools and Grassland Reserve

  1. Thank you for sharing. Dad and I enjoy looking and reading about all the flowers you post. Keep up the good work.


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