The week of Sunday, July 16 through Sunday, July 23 is Invasive Weed Awareness Week in Lake County. Invasive weeds have become a major problem throughout the state and especially in Lake County.
Just about everyone is aware of the aquatic weed problem in Clear Lake. The lake is home to an estimated 35 different species of weeds and two-thirds of them are nonnative or what are called “invasive weeds.” But not all the invasive weeds are in the lake. In fact, the county is literally being overrun with nonnative weeds and if they”re not controlled soon, it could mean thousands of taxpayer dollars spent in the future.
Some of the more invasive plants in the county are the yellow star thistle, French and Spanish Broom, salt cedar (tamarix) and arundo. All are widespread throughout the county and are causing real problems for humans and wildlife.
The yellow star thistle is the most abundant invasive weed in the county. It is a native of Eurasia and was introduced into western North America in the mid 1800s. California has more star thistle than any other state with about 15 million acres infested with the weed. In Lake County alone there are thousands of acres that are covered with star thistle and the weed continues to spread. The weed is often spread by vehicles that pick up the seeds in their tires. In fact, star thistle can even be found in the more remote sections of the Mendocino National Forest.
The mature plant is gray-green in color and grows to a height of one to three feet. Yellow star thistle is an invasive competitor to desirable plants in ranges and pastures. It can crowd out grasses where soil moisture is limited or where forage has been weakened by grazing. Where this weed is well established, its sharp spines may exclude livestock from grazing on any grasses growing beneath the star thistle plants. Yellow star thistle produces a toxin that causes death in horses through an illness called
“Chewing Disease,” which makes it impossible for the animal to swallow. The plant has little or no nutritional value to wildlife. Actually, star thistle will crowd out native forbes and other plants that deer and other wild animals eat.
The hot dry summers in Lake County are perfect for star thistle. The plant is also extremely hardy and about the only way it can be controlled is either by a strong herbicide or burning.
French and Spanish Broom are also causing all kinds of problems. These plants can grow to heights of more than six feet. These plants are also nonnative and were probably introduced as decorative plants for gardens. French Broom flowers are also used as a yellow dye for fabrics.
Salt cedar (tamarix) has replaced willows and other native plants on the shores of creeks and in wetlands. The plant uses up water and in many areas the creeks are drying up.
Invasive weeds, whether in the lake or on the land, are just another reason why we have to be diligent on what comes into the county and to protect our beautiful area.
Terry Knight can be reached at tknight3021@sbcglobal.net or by calling (707) 263-1699. Letters intended for publication that respond to Mr. Knight”s column can be sent to news@clearlakeobserver.com.
