Wildflowers of the Serpentine Realm

 

 

Can millions of years of geology create wildflowers?  In California it can, and it does!

California is geologically active.  Evidence is everywhere in Northern California.  There are mountains, volcanoes, hot springs, and even geysers! 

When people think about California geology, they think of earthquakes.  But did you know that this same geology creates stunning wildflower displays?

 

Seductive Subduction

California is a subduction zone.  Tectonic plates underneath the Pacific Ocean meet the North American Plate beneath California.  The plates with ocean above them are denser than the North American Plate.  As a result, they sink (are subducted) into Earth’s mantle.  The North American Plate rises.  Much of California was once sea floor.

 

What is Serpentine?

Serpentine is the state rock of California!  (I didn’t know there was such a thing as a “State Rock”!)  It is an attractive green color with black, and has a waxy sheen.  It is relatively soft and forms soils where it appears. 

Serpentine is created when heat and water alter igneous rock (like basalt) on the ocean floor.  After many millions of years of tectonic movement, patches of the stuff appear throughout the coastal mountain ranges where I live.

 

Serpentine and Wildflowers

Plants are sensitive to the chemistry of the soils in which they grow.  Some soils promote plant growth, others inhibit it.  Some soils are even toxic!  By looking at plant life you can learn a lot about the soil and the ground beneath.  Plants can tell stories millions of years old.

When plants grow on serpentine soil, the results are dramatic!  Serpentine soils have a large calcium-magnesium imbalance.  Just as with humans, plants need calcium to survive.  While most soils have calcium but little magnesium, serpentine soils are high in magnesium but have little calcium. 

Calcium and magnesium are chemically similar, so most plants can’t distinguish between them.  Generalist plants that try to grow in serpentine soil will take up both magnesium and calcium.  But the large amount of magnesium in the soil poisons them before they get enough calcium!¹

So serpentine soil is a niche where native Californian plants thrive and invading generalists perish.  These natives tend to be beautiful wildflowers!  So the boundary between serpentine and non-serpentine soil can be dramatic, even breathtaking.  It is like turning on a light switch.

 

Wildflower Walks

It is March and already spring has sprung.  The flowers seem to be blooming early this year.  I suspect it is due to the recent rain after a horrifically dry winter.  Also temperatures seem to be abnormally high this early in the season.

Each spring, I head out looking for serpentine wildflowers.  I choose a different location every year.  This time I joined a hike organized by Coyote Lake Harvey Bear Ranch Park.  The 4,595-acre park sits in the foothills east of Gilroy, California.  Park Ranger Chris led the hike, called Wildflowers of the Serpentine Realm.  I was surprised that as many as 30 people turned out for the hike.  Despite the large group, the grasslands are so vast that there is plenty of room for solo exploring.

Here are some pictures of the amazing wildflower displays and a Bald Eagle’s nest we found along the way.

The trailhead is at the dam that creates the lake.  Our climb to the grasslands is shaded by oaks and bay trees.

 

 

Here are some of the wildflowers we encountered in this shaded, non-serpentine, region.

 

 

 

We encountered Mulesears, a member of the sunflower family (Asteraceae).  Later this summer, I plan to post an article that shows you how to use this plant for food.

 

 

 

We climbed to grasslands, with low cumulus passing overhead in the cool morning.

 

 

 

There were a number of wildflowers growing in this environment.

 

 

 

 

We passed a large clump of pines overlooking the grasslands.  Our guide pointed out a Bald Eagle’s nest.  If you look closely at the third picture, you can see the back of an eagle sitting on the nest.

 

 

 

 

As we approached serpentine soil, the wildflower density increased.

 

 

 

Finally, we begin to see signs of serpentine soil.  Colorful wildflowers begin to replace the grasses.

I find some exposed serpentine.  It does look kind of like a snake’s skin.

 

 

 

And then the grass gives way to wildflowers…

 

 

 

 

 

 

 

 

 

 

To our delight, we see the colorful Bay Checkerspot Butterfly.  Humans have destroyed most of its habitat and it is now rare.  In fact, it is listed as a Federally Threatened Species.  These two were helping to repopulate the species.

 

 

 

 

The fields cover wide swaths

 

 

 

 

Has spring sprung near you?  Let me know in the comments below.

 

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Notes

1. The California Naturalist Handbook

 

For other interesting articles about nature, see the Nature Section and the Trips Section.