Anyone ever had an infestation of acres of these yellow plants?
http://www5.picturepush.com/photo/a/...g/13393168.jpg

They seem to be taking over my otherwise barren dry hillsides:
http://www1.picturepush.com/photo/a/...g/13393169.jpg

The plant has a strange-looking stalk:
http://www2.picturepush.com/photo/a/...g/13393210.jpg

And very low-lying leaves:
http://www4.picturepush.com/photo/a/...g/13393207.jpg

The climate is San Francisco bay area, very dry, poor Franciscan
sediment soil, and lots and lots and lots of sunlight.