Water weeds aren't the only problem
Invasive land plants such as star thistle pose huge problem across the state
June is the month when invasive weeds, both land and aquatic, start to bloom. Clear Lake is known for is weed infestation, which makes boaters very unhappy as the weeds tend to plug up their outboards and trolling motors. The county will start its annual weed spraying program on the lake within two weeks. Local lakefront property owners are also allowed to hire commercial weed exterminators to spray around their docks.
Because of the drought and low lake level, the weeds in the lake should be thicker, the reason being that the low lake level allows sunlight to penetrate to the lake bottom, which aids in rapid weed growth.
Clear Lake is home to an estimated 35 species of weeds and twothirds of them are non-native, also known as “invasive weeds.” However, not all the invasive weeds are in the lake. In fact, the county is literally being overrun with non-native land weeds and whereas some of the weeds aren't much of a problem, others can cause considerable damage.
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 can cause 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-1800's. California has more star thistle than any other state with about 15 million acres infested. In Lake County alone there are thousands of acres covered with star thistle and the weed continues to spread, often 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 such as the Snow Mountain Wilderness Area. It got to these remote areas on the hooves of pack horses and in the soles of hiking boots.
The mature plant is gray-green
in color and grows to a height of 1-3 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 and 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.
Star thistle is a longlived winter annual that is normally found below 7,000 feet elevation. The plant is very prolific in that a single plant can produce up to 30,000 seeds. The seeds germinate from fall through spring. By late spring, roots can extend down 3 feet into the ground. Just about every field in the county is infested with star thistle. It even has some defensive characteristics. When mowed the plant often creeps along the ground and blooms again. In its native land there are insects that feed on star thistle but in this country the insects have only had limited success.
French and Spanish Broom are also causing all kinds of problems. These plants can grow to heights of more than 6 feet. These plants are also non-native 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 creeks are drying up.
Invasive weeds, whether in the lake or on the land, are just another reason why we have to be diligent about what comes into the county so that we can protest our beautiful area.