Ageratum littorale (Cape Sable Whiteweed)

Native to southeastern Mexico and Central America, Florida, Cuba, and the Cayman Islands, this perennial herb grows on beaches and coastal sands. Its spreading stems rise at their tips, producing small, dense groups of lavender-blue flowerheads. Each head consists of numerous tiny florets. The fruits have a short, crown-like rim rather than a conspicuous tuft of long hairs. It is listed as Endangered in Florida, where coastal development threatens its habitat. Photographed in Florida.