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Key to Hypericum, Key A: shrubby St. John's-worts with needle-like leaves and flowers with 5 petals and 5 sepals [section Myriandra, subsection Centrosperma]

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1 Longest leaves 4-16 mm long.
..2 Upper leaf surface convex, merging gradually with revolute margins; leaves oblanceolate to linear-oblanceolate (“oblinear”); [east and west of the Mississippi River in the Coastal Plain]
..2 Upper leaf surface plane, abruptly angled to the revolute portion; leaves linear; [east of the Mississippi in the Coastal Plain].
....3 Capsules 3-4.5 (-6) mm long; longest leaves 7-16 mm long; corollas 13-17 mm in diameter; seeds reddish-amber or brown, the alveoli not in distinct longitudinal rows, the seed lacking longitudinal ridges except for the two marginal sutures; primary branches with two ridged or winged angles running the length of the internodes, extending from the leaf midribs (but not the margins) at the base of the paired leaves; leaf surface glossy; [of alfisols and ultisols of wet pine savannas, flatwoods, and seepage bogs]
......4 Plant usually branched near the base, becoming bushy and often forming a rather compact rounded shrub, usually less than 0.5 meter tall, rarely somewhat taller; inflorescence narrowly cylindric, from several of the upper stem nodes, with irregularly branched lateral clusters of flowers; seed medium to dark brown, the nearly circular alveolae not arranged in distinct lines; [SC south to north Florida and west to s MS and e. LA, usually in acidic wetland savannas and seepage slopes]
......4 Plant usually unbranched in the lower 1/3 to 1/2 of main stem length, often relatively narrow and 0.5 to 1.5 meter tall; inflorescence usually terminal, or from only the upper one or two stem nodes, obconic in overall shape, the inflorescence appearing regularly dichotomously branched; seed dark brown to nearly black, the polygonal alveolae arranged in longitudinal lines; [peninsular FL and western Cuba, usually in calcareous Pinus densa savannas and wet marly grasslands]
....3 Capsules 6-9 mm long; longest leaves 4-10 (-11); corollas 13-15 mm in diameter; seeds dark red to black, the alveoli in distinct longitudinal rows, with raised ridges often evident between the rows; primary branches with six ridged or winged angles running the length of the internodes, extending from the midribs and margins at the base of the paired leaves; leaf surface dull; [of seasonally dry spodosol pine flatwoods and interdune flats and hollows]
1 Longest leaves 13-30 mm long.
........5 Plant a low shrub, <4 dm tall, more-or-less decumbent, forming dense clumps or patches; flowers 10-12 mm in diameter; inflorescence elongate (flowers at up to 5 nodes); [of dry to mesic soils of the lower Piedmont and inner Coastal Plain from sc. VA to ec. AL; disjunct to rock outcrops of the sc. GA Coastal Plain]
........5 Plant an erect shrub, 5-40 dm tall, with single main stem branched above; flowers 13-26 mm diameter; inflorescence elongate (3-7 nodes) or short (1-3 nodes in H. fasciculatum and H. chapmanii); [of wet soils of the Coastal Plain].
..........6 Undersurface of most leaves easily visible (exposed) on both sides of the midrib, the veins usually obvious on the undersurface; leaves narrowly oblanceolate to linear-oblanceolate (“oblinear”), 1.5-5 (-7) mm wide; inflorescence elongate (3-7 nodes)
..........6 Undersurface usually not visible except for the midrib (leaf margins nearly touching the midrib for its entire length), if the undersurface visible then no veins visible; leaves linear, needle-like, 0.5-1.5 mm wide; inflorescence elongate or short.
............ 7 Plant <1 m tall; stem <1 cm wide at base; plant unbranched or few-branched, wand-like with a narrow crown; [endemic to FL Panhandle]
............ 7 Plant normally >0.8 m tall; stem 1-several cm wide at base; crown broader with many ascending to spreading branches.
............ ..8 Young branches, leaves, and sepals strongly glaucous; bark of upper stem and branches silvery gray and smooth; mature plant 2-4 m tall with ascending branches imparting a tree-like or vase-like aspect; [restricted to shores of sinkhole ponds in Bay and Washington Counties, FL Panhandle]
............ ..8 Young branches, leaves, and sepals not glaucous; bark of upper stem and branches not silvery gray and smooth (except some H. chapmanii); mature plants 0.8-3 (-4) m tall, variously shaped; [more widespread in our area, Coastal Plain of se. NC south to FL< and west to se. LA].
............ ....9 Inflorescence elongate (3-7 nodes); stem bark tight, thin, not exfoliating or exfoliating in narrow strips, grayish (not revealing buff or pale cinnamon color); leaf undersurface, if exposed at all, distinctly paler than the upper surface; [usually associated with flowing water (blackwater streams and impoundments)]
............ ....9 Inflorescence short (1-3 nodes); stem bark corky-thickened to spongy, exfoliating in broad strips or sheets revealing buff or pale cinnamon color; leaf undersurface, if exposed at all, about the same color as the upper surface; [usually associated with static water (Carolina bays, impoundments, beaver ponds, borrow pits, flatwoods depressions, cypress-gum ponds and stringers)].
............ ......10 Mature plant 2-3 (-4) m tall; branches ascending and imparting a tree-like or vase-like aspect (younger plants may be bushy); youngest internodes terete; [of flatwoods depressions and cypress-gum ponds and stringers of FL Panhandle only]
............ ......10 Mature plant 0.8-1.5 (-2) m tall; branches spreading and imparting a bushy or gumdrop aspect; youngest internodes with distinct winged ridge on either side; [of Carolina bays, impoundments, beaver ponds, borrow pits, widespread]