Sometimes, it is hard to know what plants are native to the area. If you see it everywhere, for as long as you can remember, it must be native, right?
Or maybe the weather and the soil is perfect for the type of plant, and actually it is an invasive plant — a “plant bully”, the theme for this week’s Earth-Friendly Chroniclers’ Challenge hosted by JustAnotherNatureEnthusiast.org.
When we lived in the East Bay area (Contra Costa County, California), yellow starthistles grew by the side of the road, in between paved walkways, in open fields…and in our backyard.
The spines under its bright yellow flowers were notorious for its strength and sharpness, and often flattened my daughter’s bike tires.
These thistles were brought to North America by accident in the 1800’s, and now grow in just about every state in our nation, and in Canada.
It is considered an invasive species in California, and as you can see from the first photo for this post, absolutely thrives in many parts of California.
From the California Invasive Plant Council:
Yellow starthistle is native to southern Europe and western Eurasia and was first collected in Oakland, California, in 1869. It was most likely introduced after 1848 as a contaminant of alfalfa seed. Introductions prior to 1899 were most likely from Chile, while introductions from 1899 to 1927 appear to be from Turkestan, Argentina, Italy, France, and Spain (Gerlach in prep., Hillman and Henry 1928).
By 1917 it had become a serious weed in the Sacramento Valley and was spreading rapidly along roads, trails, streams, ditches, overflow lands, and railroad rights-of-way (Newman 1917). In 1919 Willis Jepson observed its distribution near Vacaville and stated: â€œIt is 1,000 times as common as ten years ago, perhaps even six years agoâ€ (Jepson 1919).
Yellow starthistles grow and thrive all over Contra Costa County, and in particular in the Black Diamond Mine areas (part of the East Bay Regional Park District), where these photos of our dogs Jake and Sara were taken in spring and early summer.
During hikes in the summer and fall, we had to check our dogs during and after in case thistle spikes lodged near their paws, or attached to their fur.
By summer, you could see the yellow starthistle’s flowers across many of the fields and hiking trails. It crowds out native plants…and because of its long tap root, uses water that would otherwise be used by native grasses and native plants species.
It took me several years to completely get rid of it in our backyard. I don’t like using herbicides (or pesticides) so I manually pulled each one I found. Because of its long tap roots, I had to get at the base of the plant (with gloves because the rest of the plant also had sharp and itch-producing properties) and do a sort of twist and pull motion to get at it, and then dispose of it in the garbage.
With diligence, it is possible to get rid of yellow starthistles in an enclosed area, and once our garden plants and pavers were in place, I did not see anymore of it.
It’s another story in many parts of the Western United States. Again, from the From the California Invasive Plant Council:
Yellow starthistle had spread to over a million acres of California by the late 1950s and nearly two million acres by 1965. In 1985 it was estimated to cover eight million acres in California (Maddox and Mayfield 1985) and perhaps ten to twelve million acres a decade later. It is equally problematic around Medford in southwestern Oregon and in Hells Canyon in Oregon and Idaho (Maddox et al. 1985). It also infests, to a lesser degree, areas in eastern Oregon, eastern Washington, and Idaho (Roch and Roch 1988).
Aside from small-scale manual removal, other methods to control this invasive species are listed on the California Invasive Plant Council, including mechanical methods (mowing down the plants before the flowers produce seed in the summertime).
The USDA has also approved and continues to experiment with insects that attack the plant’s flowers to minimize seed production.
I’ve seen articles that indicated the yellow starthistle is poisonous to horses, but grazing by sheep, goats or cattle before seeds are formed can be an effective way to control growth if done at the right time (May and June).
Do you have an invasive plant in your area — or backyard and want to join in the WordPress challenge? Click here for details about this challenge, and visit links for the challenge guideline.
My next post will be about another invasive plant where we now live in the Central Coast of California —- the “ice plant”, which are seen along the coast and in the backyards of homes here in Monterey County.