Trichostema, Gronov.

Mcclelland, R. Kevan Schoonover, Weakley, Alan S. & Poindexter, Derick B., 2023, Seven new species of Trichostema (Lamiaceae: Ajugoideae) from the North American Coastal Plain biodiversity hotspot, Phytotaxa 603 (2), pp. 95-149 : 129-130

A new key to Trichostema section Trichostema :

1. Longest stem and node hairs three or more cells long; nodes with hairs primarily spreading, rarely also or only with hairs downwardly or upwardly curled; leaves widest towards the base or near the middle; longer style branch 1–2 times as long as the shorter ( Trichostema dichotomum complex) ......................................................................................................................................2

- Longest stem and node hairs three or fewer cells long; nodes with hairs primarily downwardly curved to appressed, rarely also with hairs spreading or upwardly curled; leaves widest near the middle or towards the tip, or linear; longer style branch 2 or more times as long as the shorter.................................................................................................................................................................5

2. Plant annual, branching primarily from the middle to upper part of the plant; mid-stem hairs spreading, occasionally also downwardly or upwardly curled, longest spreading hairs five or more cells long (view at 40x); longest node hairs five or more cells long (view at 40x), spreading, rarely also upwardly curved; nutlet ridges distinct, steep sided, giving a clearly wrinkled appearance (view at 20x; see figure 2); widespread in eastern North America ............................................................. Trichostema dichotomum

- Plant perennial, branching throughout the plant; mid-stem hairs downwardly curved, occasionally also spreading, longest spreading hairs 3–6 cells long; longest node hairs 3–6 cells long (view at 40x), spreading, rarely also or only downwardly curved; nutlet ridges fainter, shallow sided, giving a smoother appearance (view at 20x; see Figure 2 ); restricted to the outer coastal plain of North Carolina, South Carolina, Georgia, Florida, Alabama, and Mississippi .............................................................................................3

3. Older plants leggy, medium sized bushes to 1.25 meters tall; largest leaves 2.75–5.5 cm long, 0.75–1.75 cm wide; primarily inland with coastal populations in Alabama, Mississippi, Georgia, the Florida Panhandle, and Northeast Florida; not restricted to obviously calcareous substrates...................................................................................................................... Trichostema fruticosum

- Older plants compact, small to medium sized bushes to 1 meter tall; largest leaves 1–3.5 cm long, 0.5–1.25 cm wide; primarily on barrier islands of North and South Carolina or Peninsular Florida; restricted to obviously calcareous (i.e., shelly or limestone) substrates ............................................................................................................................................................................................4

4. Largest leaves 1–2.3 cm long, 2–3 times as long as wide, often elliptic to rhombic; flowers lavender to white; anthers lemon yellow; along the coast of North and South Carolina ................................................................................... Trichostema nesophilum

- Largest leaves 1.5–3.5 cm long, 2.25–3.75 times long as wide, often ovate; flowers varying shades of blue or blue-purple; anthers the same color as the upper petals; in peninsular Florida .............................................................................. Trichostema floridanum

5. Plant annual; largest leaves 2–5 cm long, 5–25 times long as wide; widespread in the Southeast.................. Trichostema setaceum

- Plant annual or perennial; largest leaves 1–3.5 cm long, 1.5–9 times long as wide; restricted to Florida .........................................6

6. Plant annual, branching primarily in the middle and upper part of the plant; largest leaves 1.8–3.5 cm long; restricted to the Florida Panhandle .............................................................................................................................................................. Trichostema latens

- Plant perennial, branching primarily near the base or throughout; largest leaves 1–2.5 cm long; restricted to the Florida Peninsula ............................................................................................................................................................................................................7

7. Largest leaves narrow, 3–9 times long as wide; nutlet ridges prominent, stocky, giving an intensely wrinkled or pockmarked appearance (view at 20x; see Figure 2 ) ..............................................................................................................................................8

- Largest leaves wide, 1.5–4.5 times long as wide; nutlet ridges faint to somewhat prominent, giving a smooth to slightly wrinkled appearance (view at 20x; see Figure 2 ) ..............................................................................................................................................9

8. Stem and node hairs primarily downwardly curved; largest leaves typically 1.5–2.5 cm long, 3.5–9 times long as wide; in mesic to scrubby flatwoods and scrub in the central to southern peninsula, not associated with the major ridge systems ............................... .............................................................................................................................................................................. Trichostema gracile

- Stem and node hairs primarily spreading to upwardly curved; largest leaves typically 1.1–1.9 cm long, 3–5 times long as wide; in sandhill and sandhill-scrub ecotones on the Brooksville Ridge and areas west........................................ Trichostema microphyllum

9. Plant branching throughout; flowering October to January; restricted to Florida scrub near Stuart and Jupiter, Florida ................... ................................................................................................................................................................................. Trichostema hobe

- Plant branching primarily near the base; flowering June to December; restricted to the large central ridge systems and associated ridge spurs (e.g., Mt. Dora Ridge, Lake Wales Ridge).....................................................................................................................10

10. Plant less robust, to 60 cm tall; leaves obovate, occasionally oblong to elliptic, very rarely ovate (5% of measured specimens); bract apices obtuse, occasionally ± 90° to rounded or acute, very rarely emarginate (5% of measured specimens); mature calyces 4.7–6.0 mm; on the Trail, Mt. Dora, and Orlando ridges and associated ridge spurs ................................ Trichostema suffrutescens

- Plant more robust, to 1 meter tall; leaves obovate or oblong to elliptic, rarely ovate (20% of measured specimens); bract apices obtuse to rounded, occasionally ± 90° to acute, rarely emarginate (11% of measured specimens); mature calyces 5.2–6.2 mm; on the Lake Wales and Bombing Range ridges and associated ridge spurs .............................................. Trichostema bridgesii-orzellii

Figures

FIGURE 2. Detail of the nutlets of Trichostema section Trichostema. A) Trichostema dichotomum, B) T. setaceum, C) T. suffrutescens, D) T. nesophilum, E) T. floridanum, F) T. fruticosum, G) T. latens, H) T. bridgesii-orzellii, I) T. gracile, J) T. hobe, K) T. microphyllum. Trichostema dichotomum (A) shows large alveoli and tall ridges. T. latens (G) shows small alveoli and shorter ridges. Photos by Derick Poindexter.