Interpretive Panel #7 – California’s Grasslands

Historical accounts from the 1800s report that California’s foothills and Central Valley contained vast stands of wildflowers interspersed with perennial bunchgrasses.  The great naturalist John Muir observed:

“Looking eastward from the summit of Pacheco Pass one shining morning, a landscape was displayed that after all my wanderings still appears as the most beautiful I have ever beheld. At my feet lay the Great Central Valley of California, level and flowery, like a lake of pure sunshine, forty or fifty miles wide, five hundred miles long, one rich furred garden of yellow Compositae.” – John Muir, The Yosemite

 
_{Early settlers marveled at the vast expanse of beautiful wildflowers that used to occur in the Central Valley.  Photo Credit: ©2015 W. Juergen Schrenk (CC BY-NC-ND 3.0)} 

In addition to those yellow composites (daisy-like flowers) that Muir loved so much, there were also millions of orange poppies, blue lupines, purple brodiaea, and pink owls clover, as well as multitudes of other wildflower species. The grasses too were quite different from those you see today.  Stands of perennial native bunchgrasses, such as purple needlegrass and blue wildrye, don’t dry up and die in late spring each year.

So, the “golden” hills of California used to be rainbow-colored all spring and stayed green well into the summer. What caused this dramatic change? 

Ecologists think that the introduction of domesticated livestock, the invasion of weedy species from Europe, and an unfortunate series of droughts all combined to utterly transform the Central Valley’s landscape. 

When hundreds of thousands of settlers moved into California during and after the Gold Rush, ranchers bred and imported millions of domesticated livestock (mainly sheep and cattle) to feed them. Since California historically contained only relatively small herds of elk, deer and pronghorn, our native grasses and wildflowers had not evolved defenses against grazing animals.  In contrast, plants from the Mediterranean area of Europe did evolve with livestock, and therefore have lots of barbs and awns to deter grazing.  (These are the plant parts that stick in your socks when you walk through a grassland.)  The newly-introduced livestock found California’s native bunchgrasses and wildflowers to be not only defenseless but also quite tasty.
 

_{Yellow star thistle, an escapee from Europe, has lots of prickly spines, unlike wildflowers native to California.  Photo credit: ©2009 Barry Breckling (CC BY-NC-ND 3.0)} 

In addition to the domesticated livestock, shipments of grain and other staples were also sent to California to feed the hungry settlers.  Some of these shipments inadvertently contained seeds from some of those well-defended European plants, including rip gut brome, yellow star thistle and foxtail. (Even their names sound prickly!) These invasive plants had a huge competitive advantage over native plants because they were not as heavily grazed due to their prickly defenses.  They quickly spread throughout the valley, displacing native plants.

Finally, a series of severe, multi-year droughts in the 1850s and 1860s also had a detrimental impact on California’s native prairies. The new invading weeds were mostly annuals, and they set seed in late spring each year and die shortly thereafter.  These species survive our hot, dry summers in the form of a dormant seed, ready to sprout when the fall rains arrive.  In contrast, most of California’s native grasses are perennials.  They live for dozens of years and rely on their deep roots to get through dry summers.  The multi-year droughts hit them much harder than the non-native annuals.

It is this critical combination of selective grazing by large herds of livestock, competitive pressure from invasive annual weeds, and severe multi-year droughts that caused the Central Valley to change over a 30-year period in the late 1800s from a diverse, flower-filled prairie to the bland annual grasslands we have now.

 
_{Ithuriel’s spear is one of the lovely California native wildflowers that still occurs in Centennial Park.  Photo credit: © David Davies}

Luckily small patches of wildflowers still exist, and the harvest brodiaea, white brodiaea, Ithuriel’s spear and spikeweed found throughout Centennial Park remind us of what the Central Valley used to look like.  In addition to these remnant naturally-occurring wildflowers, the Centennial Park Restoration Project seeded 10 species of native grasses and 20 species of native wildflowers over a 14-acre area. Projects like this one are helping to restore some of California’s unique and beautiful prairie ecosystem.

This information has been provided by the City of Vacaville in partnership with the Solano Resource Conservation District.  It was last updated on May 21, 2020.