I collected and scattered a few Texas Thistle, Cirsium texanum, seeds in my front garden last year.
Since Texas Thistle is a biennial, the seeds sprouted and grew into small plants last year. This plants bloomed this year and will later die.
The flowers attract a number of pollinators. If the flowers are left on the plant, the seeds will be eaten by goldfinches (I read this on the internet and do not have first hand experience). Additionally, the plant is said to be a host plant for painted lady butterfly caterpillars.
Like many plants, Texas Thistle grows much taller in my garden than it does in the wild. It is hard to tell in this picture, but the Texas Thistle in the background is over 6 feet tall. The other plants in this photo that look kind of like a thistle are American Basketflower, Centaurea americana.
I have grown American Basketflower for several years. American Basketflower is an annual and needs to go to seed in order to come back the next year. Most of my plants produce flowers that are light pink in color.
I added seeds from plants with darker colored flowers a couple of years ago so now I have a wider range of colors. This is not a great photo, but it shows some of the variations in colors.
Here is a close up of one of the darker American Basketflowers.
American Basketflowers and Texas Thistles are both in the Aster family. It is pretty easy to differentiate the two plants. American Basketflower gets its name because the bracts under the flowerhead look like a basket. The bracts are stiff, but not prickly.
Texas Thistle has little spines below the flowerhead.
The leaves of American Basketflower are soft and spineless.
By contrast, the tips of each lobe of Texas Thistle terminates in a point. Gloves are highly recommended when handling this plant.
I will probably remove any new Texas Thistle seedlings that pop up in the front garden and scatter some seeds in the backyard because the plant is a little too tall for the front yard. I will be removing the older seedheads soon because I do not want the plant to take over.