Stout jointweed

Thysanella robusta Small, Bull. Torrey Bot. Club 36: 159. 1909; Polygonella fimbriata (Elliott) Horton var. robusta (Small) Horton

Herbs, annual or perennial, gynomonoecious, 5-11 dm. Stems erect, usually branched at base, sometimes simple, glabrous or sparingly scabrous on angles distally. Leaves persistent; ocrea margins ciliate; blade linear, (10-)25-43(-69) × 1.2-2.5(-3) mm, base barely tapered, margins hyaline, apex acute to acuminate, glabrous. Inflorescences (10-)20-50(-60) mm; ocreola encircling rachis, only the base adnate to rachis, apex acuminate. Pedicels spreading in anthesis and fruit, 0.3-1 mm, much longer than subtending ocreola. Flowers bisexual or some pistillate, these usually distal; outer tepals loosely appressed in anthesis and fruit, pink to white, drying orange, ovate, 1.7-4.5 mm in anthesis, margins erose; inner and transitional tepals pink to white, drying orange, loosely appressed in anthesis and fruit, oblong, 1.8-3.8 mm in anthesis, margins deeply fringed; filaments monomorphic; anthers pink; styles and stigmas 0.7-1.5 mm in anthesis. Achenes usually included, sometimes exserted distally, yellow-brown, 3-gonous, 1.8-2.6 × 1-1.5 mm, shiny and smooth proximally, dull to shiny and minutely roughened distally. 2n = 32.

Flowering Jul-Dec. Sandy roadsides, waste places, scrub; 0-60 m; Fla.

Polygonella robusta is closely related to P. fimbriata and has been treated as a variety thereof. Differences in morphology and distribution provide a basis for treating the two taxa as separate species (G. L. Nesom and V. M. Bates 1984).