This plant is a member of the Asteraceae (Aster or Sunflower) family, and is a native to the Mediterranean. The plant is also known as golden starthistle, yellow cockspur.
As pretty as the pineapple crowned cotton-fuzzy cluster is, the plant itself is a tangled web of stems. This plant is a common weed, so common in California it rules the fields. Threatening the open range of Washington and Idaho, Montana is monitoring the spread and has an infestation alert to keep it from invading it's state. The seeds of this plant are carried away by the drift of the wind and quickly take root where it lands. It's a deep rooted and difficult to uproot.
The Yellow Star Thistle most-likely was imported to California from the Mediterranean during the California Gold Rush, in contaminanted grains such as Alfalfa feed.
The long sharp thorns are the plants 'warning' to four-legged creatures to stay away! This plant is especially toxic to horses; one bite and it paralyzes the horses mouth and can kill them and it's deadly to many other animals as well.
This plant is not like the 'Milk Thistle' used in herbal remedies, stay clear of this one.