I am looking for a good bee plant that will grow in wet, acidic, clay soils in zone 4. Does anybody have any experience with this or suggestions - other than swamp milkweed? Swamp milkweed is supposed to be good, but it is considered toxic to mamals and spreads rapidly. The area around where I want to plant these flowers is used for hay and therefore it would not work to have milkweed spread into the hay field. Thank you for any help.