hoping to identify stinging plant

Hi Nick,

You may address this nasty plant as Canada Thistle. It is a thug.
CSU Master Gardener Boulder County has a fact sheet on the Canada Thistle. I am an apprentice and this is my 2nd time on the desk so I beg your forbearance as I am unsure if, the link below will access the fact sheet.
http://articles.extension

Ask an Expert is available to you at any time. If, you have further questions in addition to the identification of the plant please contact us again. I hope this helps.
Add my curse too!

Hi Nick:
It definitely looks like a type of thistle. Often thistles have bright pink flower heads.
With the picture, its hard to see but I think I can see a small yellow flower head, if so
it could also be a type of Sowthistle. The stem would also contain a milky juice.
Thistles are considered a noxious weed in colorado.
Watch it mature to see what color the flower head is.

Thanks for the quick replies. I'll post another picture when it blooms. Actually, I should have include something for scale -- I think it's small compared to Canada thistle (this is "adult size"). The leaves don't quite look like sow thistle pictures on the internet, but there's a lot of variation.

Hi Nick,
A more mature picture would be very helpful in determining the type. The flower color is important.

Here's a better picture, showing how small it it. Perhaps yellow towers budding - tiny!

-Nick

Found it: desert tragia, or branched noseburn! What a name. Apparently some varieties sting more than others. https://www.backyardnature.net/n/h/noseburn.htm