Yellow Star Thistle and the Reticular Activating System

Invasive plants and motivational seminars collide in my world.

If you’ve ever attended a goal-generating seminar, you’ve probably heard the term Reticular Activating System (RAS) tossed around. It’s used in motivational circles to describe our physiological capacity to pay attention. The RAS is part of a large network in our nervous systems, controlling consciousness, sensory input and attentiveness. Because of that, RAS is often used to describe the phenomenon of selective attention: that is, you buy a black Honda and suddenly, you notice all of the black Hondas on the road.

Or, you happen to see some goldfinches feeding on thistle plants which inspires curiosity — and suddenly, you’re surrounded by thistle, more thistle than you ever imagined existed on this planet. Vast plains of thistle.

Hugh and I took a hike in Briones Regional Park the other day and the first thing we noticed was the dead thistle. Artichoke Thistle (Cynara cardunculus). Fields of brown, crumbling thistle. We assumed the plant deaths were part of a thistle eradication program.

Interspersed with the dried plants were thriving bunches of Yellow Star Thistle (Centaurea solstitialis L).

In some areas, the Yellow Star Thistle was a field unto itself.

In parks like Briones, a number of measures have been used to eradicate and control these thistle plants. Methods include spot herbicide treatments, cutting, burning and even using grazing goats to reduce the plant populations. Although this thistle is toxic to some animals (like horses) apparently, goats can handle the digestion well. I’m not sure and could not confirm if these goats at Briones were being used for thistle eradication or for fire prevention. Both goals are accomplished with the goats and their predictable appetites.

In one area of the hike, the Artichoke Thistle was slain and broken, creating a thick mat with just select plants left standing. The standing plants gave these young Western Bluebirds (Sialia mexicana) some handy elevation.

The stalks crisscrossed on the turf made for surprisingly good cover for the juveniles and adults alike. This image is deceiving in a way. The bluebird stands out in this close crop. In the vast field, there were numerous birds skulking among these stalks without much notice from anyone but us.

I’m now certain my Reticular Activating System will never again be able to filter out thistle. It may be the price I’m paying for my ardent defense of California’s non-natives.

Related post: The Goldfinch and Thistle (A Pub With No Pints)