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About 16 inches tall, with small 5- petal white flowers and spiny leaves.
Desert habitat, about 6500 feet above sea level.
Just a note - the picture in the Wikipedia article is misleading - the leaves of C. stimulosus are indeed toothed and spiny, like your picture. The flowers are no more than half an inch across. Anyway, good luck finding a positive ID!
I don't think it's Cnidoscolus stimulosus, since its leaves are toothed and the flowers are quite small. Thanks, though. :)
If this isn't stinging nettle, it sure looks a lot like it. I don't suggest touching it to find out for sure, though!