Recent Examples on the WebSome perennials such as Zagreb threadleaf tickseed (Coreopsis verticillata) will continue to expand and take over sections of your bed without occasional dividing. Tim Johnson, chicagotribune.com, 16 Apr. 2022 These included milkweed, tickseed, corkystem passionflower, firebush, Virginia snakeroot and blue porterweed. Amanda Klarsfeld, sun-sentinel.com, 23 Sep. 2020