The Bull Thistle, a member of the Sunflower Family (Asteraceae), is an extremely prickly plant that should only be handled with gloves - heavy gloves. Believe me, I have had a good deal of experience with these!! They are one thing that does grow well in my yard! They grow in profusion along roadsides, pastures and weedy areas. The plants are large, and can grow to 6 feet tall. The flowers bloom from June through September through out the United States.