Can you ID the little yellow globe flowers? The leaves are thin and frilly or lacy. The leaves and stems have a smell reminiscent of tomato plants, very pungent. If left alone, it can develop into a thick cluster of stems several feet across, as in these pictures.
My family calls it Tansy, but common tansy (tanacetum vulgare) is too flat. This is spherical but slightly oval, in other words elongated upwards, you could say slightly conical. Tanacetum vulgare looks quite similar, but it isn't spherical and the foliage is also different. Please look at the original photo in other post, "Yellow / red flower". Please ask if you need another photo to ID.
How about Matricaria matricarioides, (syn. Matricaria discoidea) Pineapple weed? Several pix at this site to compare (spelled incorrectly at that site). http://www.wildmanstevebrill.com/Plants.Folder/Pineappleweed.html
Boy, that's awfully close. It looks like this one does in beginning budding stages, but the scent is definitely NOT pineapple, it's more like tomato *plant* (pungent, acrid). Also, the flower cone is a little taller. See the original picture under the "Yellow / red flower" (Gaillardia aristata) post. The bottom right of that pic shows a good profile view. I believe we also have pineapple weed here, though I haven't seen any for a while. This is different. It looks an awful lot like chamomile without the petals. You may have pinned the genus, but I'm not coming up with anything just like it in a Google image search on matricaria. It's a hardy weed, with powdery seeds (the flower/seed head has hundreds of seeds).
Bingo! Thanks, Tipularia. The description, pictures, and all fit to a T. Even nicknamed "Stink Net", as well as Globe Chamomile. Asteraceae family. Introduced from S. Africa, cultivated in Phoenix, AZ, and now escaped and spreading invasively and rapidly. Grows well in dry, hot climates (such as ours). We get large stands of this stuff, hard to get rid of it because it has hundreds of seeds on hundreds of heads in each stand. It seems toxic from its smell. How would I find out about toxicity? Thanks again.