What kind of thistle is this?

Question

I'm doing a wildflower collection for PreAP Biology, and I found this flower which I'm pretty sure is some kind of thistle. I found a picture of it, and the site says that it's yellow thistle, but when I type in yellow thistle on google, I get a different flower. Does anyone know what kind of flower this is:

http://www.texaswildflowerpictures.com/wildflowers/yellowthistle.jpg

Thanks

Answer 1

It is more likely to be a milk thistle

Answer 2

Check this out: (some purple thistles are yellow) : http://plantatlas.usf.edu/image.asp?imag...

Here's a yellow: (....ish)http://plantatlas.usf.edu/image.asp?imag...

Sow thistles are bright yellow:

http://plantatlas.usf.edu/image.asp?imag...