It is said that they repel fleas hence the name. It is a common weed variety in untreated lawns and right of ways. There are over 150 varieties of this plant in N. America. I had a single plant that I allowed to grow in my back yard 3 yrs ago. The clump is now about 16 inches wide. It blooms every spring for several weeks. After the blooms fade I mow it down and enjoy it again the next year.