Hypericum densiflorum (Nomenclature)
Shrub 0.6-3 m tall, erect, with branches erect, rather stiff, numerous, forming rather slender bush, but with adventitous shoots from roots sometimes producing extensive thickets. Stems green to reddish, 4- lined and ancipitous when young, soon 2-lined and rounded, becoming reddish brown and terete in 2nd season; cortex exfoliating in strips; bark smooth, thin. Leaves sessile, sometimes in immature clusters in leaf axils; lamina 20-40.5 x 2-7 mm, very narrowly elliptic-oblong or oblanceolate to linear, with margin recurved to revolute, paler and often glaucous beneath, chartaceous, deciduous at basal articulation, apex apiculate or apiculate-obtuse to subacute, base narrowly cuneate to attenuate; venation sometimes obscure beneath: c. 14-17 pairs main laterals, with subsidiaries and tertiary reticulation sometimes visible, only midrib prominent; laminar glands dense. Inflorescence c. 5-25-flowered, without accessory flowers, with (2-)5-15-flowered dichasia from 1-2 nodes below and sometimes flowering branches from lower nodes, the whole broadly pyramidal to broadly cylindric or obpyramidal; pedicels 0.5-5 mm long; bracts reduced, oblanceolate- spathulate to linear. Flowers 10-17(-20?) mm in diam.; buds broadly ovoid-ellipsoid. Sepals 5, (4-)4.5-6 x 1-1.5 mm, unequal or subequal, not enlarging but divergent to reflexed in fruit, narrowly oblong- lanceolate or narrowly oblong to oblanceolate-spathulate, subacute or apiculate to acute, margins revolute, basal veins 1-3, the laterals sometimes branched. Petals 5, deep golden yellow, becoming (incurved-) deflexed, 6-9 x 2.5-3.5 mm, obovate-oblanceolate with apiculus lateral, acute. Stamens c. 100-150, longest 4. 5-7 mm, c. 0.8 x petals. Ovary 3^(-5)-merous, 3-3.5 x 1-1.3 mm, narrowly pyramidal-ovoid, acute; placentation incompletely axile; styles 3- 4(5), 2-3 mm long, 0.7-0.85 x ovary, remaining erect, separating only as fruit matures. Capsule 5-6(-7) x 2-3 mm, narrowly ovoid-conic or narrowly ovoid to cylindric-ovoid, acute, not or scarcely lobed, exceeding sepals, thinly coriaceous. Seeds reddish brown, 0.8-1.3 mm long, not carinate; testa linear-reticulate.
2n = 18 (n = 9) (Adams in Robson & Adams, 1968). Adams also reported 2n = 27 (n = 11-14) in one population due to unequal segregation (Adams, 1959)
Wet or moist habitats (meadows, lake margins, open stream banks, pinelands, bogs, ditches), also on dry road embankments and rocky hillsides; lowland to c. 1000 m.
Eastern U.S.A. from central Georgia northward along the coastal plain to New Jersey and thence south-westward along the Appalachian Mts from Pennsylvania to northern Georgia and central Alabama.
Despite the existence of some intermediate populations, it seems best to maintain 5. H. denslflorum as specifically distinct from 4. H. lobocarpum (q.v.). H. densiflorum usually has a trimerous ovary, but 4- or 5-merous ovaries may also be present on the same plant. The capsule is usually but not always unlobed. However, except for members of the intermediate Alabama populations, it is nearly always possible to allocate a specimen to one or other species. Whereas the south-westernmost (Alabama) populations of H. densiflorum verge morphologically towards H. lobocarpum, some in Tennessee and northern Georgia with narrow leaves and narrow, small-flowered inflorescences (H. interior Small) tend towards H. galioides. H. densiflorum is apparently always distinguishable in the wild from 2. H. prolificum by the smaller, more numerous flowers and fruits in a shorter and relatively broader inflorescence. In cultivation, however, these distinctions may be far less clear (see below).
Adams (1973) reported evidence of poor seed production in some populations, a condition that, he suggested, might be correlated with the occurrence of triploidy (see above).
Rehder interpreted his H. nothum specimens as hybrid (H. densiflorum x kalmianum) on account of the occurrence of a few 4- or 5-styled capsules among the predominantly 3-styled ones. Despite these, however, as Adams pointed out, the specimens can readily be assigned to H. densiflorum.