Ask a gardener about planting thistle, and they will most likely tell you not to plant it--it is a weed. Ask a bird-watching enthusiast and they will tell you that planting thistle is a great way to attract birds like finch and woodpecker who dine on thistle seeds. The herbalist will tell you that thistle has medicinal powers, like using milk thistle extract to counteract mushroom poisoning. Butterflies are attracted to the blooms of thistle plants for the benefit of the butterfly lover.
Harvest thistle seed. It is unlikely you will find a location to buy thistle seed since it is considered an invasive weed. In the fall, collect seeds from wild thistle and spread it out on a flat surface to dry for about one week. Store the seeds for the winter in a plastic bag kept in the freezer.
Remove the seeds from the freezer in late winter and keep in a cool dry place, like in a garage or basement.
Choose a full sun area in the spring to plant the seeds. Rake the soil. The area does not need to be free of grass, but working with soil with no grass or weeds will make it easier to see the new growth for thinning.
Moisture the raked soil and then disperse the seeds. Cover them with about 1/8 inch of soil. No need to sow the seeds in straight lines unless desired.
Thin to about 10 inches apart when the seedlings are about 2 inches tall by gently pulling out the weaker plants.
Continue to water regularly through the growing season, about every five to seven days if there is no rain.