Glandularia bipinnatifida (Prairie Verbena)

Native to the central and west-central United States and northeastern Mexico, this low herb or subshrub spreads through reclining stems that may root where they touch the ground. Opposite leaves are deeply divided into narrow, toothed segments. Hairy, four-sided stems carry compact flower spikes that appear flat-topped while blooming and lengthen as fruits develop. Fragrant, narrow-tubed flowers open into five spreading pink to purple lobes. Each fruit separates into four small, dry nutlets. Its flowers provide nectar for butterflies and bees. It has been introduced to Germany and Nicaragua. Photographed in Colombia.