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Key to Trichostema

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1 Leaves strongly three nerved from the base, the nerves approaching the midvein near the tip of the leaf; calyx and corolla nearly actinomorphic; [mafic or calcareous habitats (e.g., diabase, limestone)]; [section Isanthus]
1 Leaves without strong lateral nerves; calyx and corolla clearly zygomorphic; [habitats various]; [section Trichostema]
  2 Stem and node hairs medium length to long, typically three or more cells long; node hairs primarily spreading; leaves widest towards the base or near the middle; longer style branch 1-2× as long as the shorter branch; [Trichostema dichotomum complex].
    3 Plant annual, branching primarily from the middle to upper part of the plant; node hairs long, spreading or upwardly curved, to more than five cells long, the cells short (view at 40× magnification); nutlet ridges primarily medium-sized, occasionally tall; [widespread in our region]
    3 Plant perennial, branching throughout the plant; node hairs of medium length, spreading or downwardly curved, to 3 cells long, occasionally long, but with six or fewer elongated cells (view at 40× magnification); nutlet ridges primarily short, occasionally medium sized.
      4 Older plants leggy, medium sized bushes to 1.25 m tall; largest leaves 2.75-5.5 cm long, 0.75-1.75 cm wide; [primarily occurs inland with coastal populations in s. AL, s. MS, e. GA, FL Panhandle, and ne. FL, not restricted to obviously calcareous substrates]
      4 Older plants compact, small to medium sized bushes to 1 m tall; largest leaves 1-3.5 cm long, 0.5-1.25 cm wide; [primarily occurs on barrier islands of NC, SC, or peninsular FL, restricted to obviously calcareous (i.e., shelly or limestone) substrates.
        5 Largest leaves 1-2.3 cm long, 2-3× as long as wide, often elliptic to rhombic; corollas lavender to white; anthers lemon yellow; [e. NC and ne. SC]
        5 Largest leaves 1.5-3.5 cm long, 2.25-3.75× as long as wide, often ovate; corollas varying shades of blue or blue-purple; anthers the same color as the upper petals; [peninsular FL]
  2 Stem and node hairs short, typically three or fewer cells long; node hairs primarily downwardly curved to appressed, rarely spreading; leaves widest near the middle or towards the tip, or linear; longer style branch 2× or more times as long as the shorter branch.
          6 Plant annual; largest leaves 2-5 cm long, 5-25× as long as wide; [widespread in our region, south to c. peninsular FL]
          6 Plant annual or perennial; largest leaves 1-3.5 cm long, 1.5-9× as long as wide; [FL]
             7 Plant annual or perennial, branching primarily in the middle and upper part of the plant; largest leaves 1.8-3.5 cm long; [FL Panhandle]
             7 Plant perennial, branching primarily near the base or throughout; largest leaves 1-2.5 cm long; [FL peninsula].
               8 Largest leaves narrower, 3-9× as long as wide; nutlet ridges tall, occasionally medium-sized.
                 9 Stem and node hairs primarily downwardly curved; largest leaves typically 1.5-2.5 cm long, 3.5-9× as long as wide; [mesic to scrubby flatwoods and scrub in the central to southern FL peninsula, not associated with the major ridge systems]
                 9 Stem and node hairs primarily spreading to upwardly curved; largest leaves typically 1.1-1.9 cm long, 3-5× as long as wide; [sandhill and sandhill-scrub ecotones on the Brooksville ridge and areas west to the coast]
               8 Largest leaves wider, 1.5-4.5× as long as wide; nutlet ridges short to medium-sized.
                   10 Plant branching throughout; flowering Oct-Jan; [narrow strip of scrub between Stuart and Jupiter, FL in Martin County]
                   10 Plant branching primarily at the base; flowering Jun-Dec; [large central ridge systems and associated ridge spurs (e.g., Mt. Dora Ridge, Lake Wales Ridge)].
                     11 Plant less robust, to 6 dm tall; [Trail, Mt. Dora, and Orlando ridges and associated ridge spurs]
                     11 Plant more robust, to 10 dm tall; [Lake Wales and Bombing Range ridges and associated ridge spurs]
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