Star of Bethlehem (Ornithogalum umbellatum) used to be a pretty bedding plant, but has now gotten into yards and is all but impossible to kill. Besides multiplying like crazy, the problem with it is that all parts of the plant and bulb are toxic. The leaves look a lot like wild onions (but no odor), and the flowers are small, white, with 6 petals. I'm sweating the next couple of days out as my hens ate a lot of them today when I was doing yard work. I just read several posts online about dogs and goats dying after eating them. I just lost one hen to what looked like cardiac failure---could have been this. I can't stand the thought of more losses. Wish I'd known that the plant was toxic before now.
http://www.btny.purdue.edu/weedscience/2005/starofbeth05.pdf
http://www.btny.purdue.edu/weedscience/2005/starofbeth05.pdf