In the front part of our pasture, right by the tack room end of the barn, there is growing a rather odd looking weed.  The soil is very poor there, pretty much all clay, so not too much grass has grown, and there are always plenty of small rocks.  The alpacas come up here occasionally and do find something to eat, but they've never touched this weed.  So I'm guessing they know it's either bitter tasting and/or poisonous to them.  Guesses anyone?

Yes, folks, I realize the picture is sideways!  It was the best way to get the entire plant in the picture.  It's about to flower some little yellow flowers.  This plant really is pretty but I need to pull it out soon before it goes to seed, just in case it really shouldn't be in an alpaca pasture.  And yes, that's grass you see around it.  This is right near an area that the alpacas have designated a(nother) poop pile.  Now that I think of it, perhaps it was some sort of seed in their hay; maybe that's how it's gotten here.  It's the only  one we've seen around our entire property.

If you know what it could be, please comment to let me know!  I'll be very grateful!  Thanks everyone!