Are There Any Poisonous Thistles?

Are There Any Poisonous Thistles? Are there any poisonous thistles? Milk thistle, a regulated Class A noxious weed, is a toxic, branching winter annual or biennial that grows 2-6 feet tall in disturbed areas, such as pastures, roadsides, ditches, and fencerows. Ingestion can cause nitrate poisoning in cattle and sheep. Are all thistles edible? All