Distaff thistle (Carthamus lanatus) - I've trained cows to eat this weed
Other Common name(s): saffron thistle, false star thistle, woolly safflower, woolly star thistle, downy safflower
       This native of the Mediterranean region is a spiny annual that can grow up to 3 1/2 feet tall. We know that efforts to control the thistle began as early as 1871 in Australia, but in spite of their ongoing efforts, it is still reported in every Australian state (1). For more on the plant itself, download this Fact Sheet from Oregon.
        Nutrients: Peggy Rathmann harvested a late-growing distaff thistle in October and had it tested for nutritional value at Utah State University. It compared favorably with the nutritional value of Alfalfa, and contained 17% crude protein, 34% NDF and 57% TDN.
       Toxins: There are no known incidents of poisoning due to distaff thistle. Based on a report by San Feliciana, et al. (2) the plant contains sesquiterpene glycosides. This is similar to what is found in spotted knapweed which cows were successfully trained to eat at Grant-Kohrs Ranch national historic site. In general, animals are more successful eating terpene-containing plants when they have adequate protein.