yellow joyweed, Alternanthera flavescens

Yellow joyweed is one of about 90 species of Alternanthera. Most of those grow in tropical America, and nine have made it here. But when? Some authorities believe yellow joyweed is an introduced species, but it was one of the first species recorded when the flora of Florida began to be explored. So others believe this is native. Yellow joyweed occurs in such a wide variety of habitats in FL that it does appear to be weedy. All flowers are a joy to see, but beyond that I haven't discovered how this plant earns that name. Miami-Dade Co FL, 3/21/16. Amaranth family, Amaranthaceae.