Yellow Starthistle: Invasive plants and the Earth-Friendly Chroniclers’ Challenge

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?

Field of Yellow Starthistles

Field of yellow starthistle – Photo via (Creative Commons) by Joseph M. DiTomaso, University of California – Davis, – See more at:

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

Yellow Starthistle Detail

Photo – Creative Commons by Stephen Ausmus, USDA Agricultural Research Service, – See more at:

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: “It is 1,000 times as common as ten years ago, perhaps even six years ago” (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.

Jakey Boy

Jake — our black lab mix and best pound dog ever!

Sara Sassafras

Sara — the smallest, and sweetest Newfoundland…

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.

Jake and Sara Contra Costa County hike

Our dogs Jake and Sara — ahead of us in scenery typical of Eastern Contra Costa County, California. By summer, many fields (like this one) will be blanketed with yellow starthistle flowers…establishing itself in wider and wider areas…

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.

Garden area

After pulling out yellow starthistles from the backyard, we eventually had a decent garden and patio area. Photo of the garden area by the side of the house is of my daughter (in the middle) her friend, Jennifer at right, and our dog, Sara to the left.

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.


Photo of horse taken at a ranch in Placer County, near the Sacramento Metropolitan area.

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.

14 thoughts on “Yellow Starthistle: Invasive plants and the Earth-Friendly Chroniclers’ Challenge

  1. I always ponder the expression “A weed is just a plant in the wrong place”! Your star thistle looks like a nasty piece of work in any place, but those spikes must have had a purpose originally – not just deflating tyres. Makes you wonder what it was 🙂

    • I suspect the spikes were to thwart animals from eating the flower — it really is incredibly sharp, I hated those plants and happy to NOT see them in this part of California —- at least for now. We don’t have the super hot summers here, like in Contra Costa County, our past home.

      It reminded me of the spikes on the rattan palm plants, which was also a sort of deterrent for animals (I posted about rattans before…on a photo challenge WRONG 🙂

      By the way, it is interesting to see the different spellings of English words…like colours…and tyres!

      • Good explanation for the spikes, thank you. I have also been injured by date palms and others. Yes, we still honour our British heritage. We even have an ‘h’ on all our verandahs. 🙂

  2. Lola Jane-
    The Yellow Starthistle is listed in our EDRR Booklet for the Tualatin Valley. Now I can see why it is a plant of extreme concern. The photos in your post vividly show how dense an invasion of Yellow Starthistle can be. We don’t have anything like that happening in our part of the state, however, data from Oregon State University matches the stats you shared from the California Invasive Plant Council. Medford and areas along the Columbia River / Snake River in Northeastern Oregon have experienced problems.

    I’m impressed that you were successful with hand-pulling to remove this invasive from your yard. That is such HARD work that requires persistence. I can empathize from the perspective of using the same technique on our property with Himalayan Blackberries, Canary Reed Grass, and Lesser Celandine. Your no- chemical approach is one I whole-heartedly agree with. Isn’t it wonderful to know that the birds and critters that come to your yard aren’t facing chemicals?

    Thank you for exposing a plant-bully!


  3. Thank you for the link to the write up by Oregon State, Jane… once the infestation begins, it is hard to control, so I do hope the problem does not worsen in Oregon.

    I think the weather in certain parts of California, like where we use to live, is perfect for this plant as it loves summer heat / droughts…so maybe they’ll survive our drought years more so than native plants… 🙁

    Definitely, we all need to think twice (or more) before using pesticides and herbicides, or just say no to them. I had problems with snails and slugs, and use to hand pick them at night with a flashlight, and have done the “beer” in the pie pan trap, too.

    This is a great challenge, that many can relate to, and I’m so glad to see this Earth-Friendly focused blog challenge evolve, especially with the new name, Jane <3

    By the way, I read on your Oregon link that goats are able to munch on these thistles even after the flowering stage, as they can chew on those sharp spikes with no problem...Go Goats!!! I do remember now that even past May / June, they were trying to control infestations in parts of Contra Costa and neighboring counties through bringing herds of goats to mow down fields. Food for goats, and environment friendly controls...always a good thing.

  4. I don’t think I’m familiar with these plants. Monterey County weather isn’t conducive to these pests? But, oh yes…iceplant…we used to have a ton covering my parents’ backyard. Look forward to reading about these plants in your next post.

    By the way, thank you for another reason for wanting a goat!

    • I am AMAZED that goats can chew on those spikes…flattens bicycle tires, but food for goats? No problem.

      I am happy to NOT see these nasty thistles here, I think they like warm weather, and dry summers. Thank you Monterey Bay fog! Yes, iceplants are another story, and I’ll post that soon after I edit the photos.

    • By the way, parts of Sonoma County inland have similar weather to Contra Costa County, so I think you will eventually run into these plants on your hikes at more inland spots (unfortunately). And if you do, take a picture and post to link to this challenge! Or maybe…. Sonoma County had better success at controlling them.

        • I hope the yellow starthistles did not make it over to Sonoma County… they don’t flower until summer, so perhaps you’ll see some in the coming months, and in that case, yes, definitely go full Terminator on them!

    • Lastly, unlike the official California State flower, the poppy with its $1,500 fine for picking, I think it is safe to say you are allowed to pick, pull, and to stomp on yellow starthistle flowers. Just be sure you dump the seeds / flowers in the trash 🙂 or they’ll just germinate next spring. Each flower head can contain up to 80 seeds.

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