Updated May 12 2021: This thistle was initially misidentified as Italian Thistle, Carduus pycnocephalus. It is Slenderflower Thistle, Carduus tenuiflorus, a close relative of Italian Thistle, with the same noxious qualities. The two species are commonly confounded.
Thick and sticky thistle No. 2: Slenderflower Thistle, Carduus tenuiflorus. This one has pink flowers and more spines than it knows what to do with. There is no question of eating this one. Cattle can’t graze on it, and where it grows densely it keeps animals from grazing on good forage nearby. There’s no split of opinion on this one. It’s officially declared a noxious weed in Australia, New Zealand, Micronesia, South Africa, the Arabian Peninsula, South America, Hawaii, and North America, especially California, where the Department of Agriculture considers it a C-listed weed. The California Invasive Plant Council rates it a Limited Invasive. It’s often found in “disturbed areas.” It can’t be killed by mowing or slashing. The root has to be severed at least four inches below ground to keep it from coming back. Nice plant. Don’t you want to take a clipping and plant it in your garden?