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round-fruit St. John's-wort, roundseed St. Johnswort

Carolina St. Johnswort

Habit Herbs (perennial) or subshrubs, erect or decumbent, not or rarely rhizomatous, unbranched or branched proximally, 2–6 dm. Shrubs, erect, forming dense thickets, 3–45 dm, bark smooth, not metallic-silvery.
Stems

internodes 2–4-lined.

internodes 4-lined at first, becoming 2-winged, then terete.

Leaf

blades narrowly elliptic or narrowly oblong to linear, 30–70 × 3–15 mm, base not articulated, narrowly cuneate to linear, margins plane to revolute, apex subacute to rounded, midrib with 0–4 pairs of branches.

blades linear or linear-subulate, 9–26 × 0.5–1.5 mm, base articulated, narrowly cuneate or parallel, margins revolute, apex rounded or acute to long-acuminate with prominent hydathode, midrib unbranched.

Inflorescences

rounded-corymbiform, 7–70-flowered, narrowly branched, sometimes with dichasia or branches from to 8 proximal nodes.

narrowly to broadly cylindric, 3–15-flowered, sometimes with 1–3(–7)-flowered dichasia from to 6 proximal nodes, sometimes with 1–2 pairs of additional flowering branches.

Flowers

10–15 mm diam.;

sepals persistent, not enclosing capsule, 5, broadly ovate to oblong-elliptic, ± unequal, 2.5–5 × 1.5–3 mm;

petals 5, bright yellow, oblanceolate-elliptic to elliptic, 5–9 mm;

stamens persistent, 45–85;

ovary 3-merous, placentation parietal.

10–18 mm diam.;

sepals deciduous, not enclosing capsule, 5, linear-subulate, unequal to subequal, 3.5–7 × 0.4–0.8 mm;

petals 5, yellow, obovate to elliptic-lanceolate, (5–)6–10 mm;

stamens deciduous, 50–80(–115);

ovary 3-merous;

styles shorter than ovaries.

Capsules

broadly ovoid to depressed-globose, 4.5–8 × 4–7 mm.

narrowly conic to cylindric, (4.5–)5–7 × (1.3–)2–3 mm.

Seeds

carinate, 2–2.7 mm;

testa coarsely reticulate.

scarcely carinate, 0.5 mm;

testa finely reticulate.

Hypericum sphaerocarpum

Hypericum nitidum

Phenology Flowering summer (Jun–Aug).
Habitat Rocky outcrops or embankments, prairies, stream banks, usually wet or moist, railroad embankments
Elevation 500–1000 m (1600–3300 ft)
Distribution
from FNA
AL; AR; IA; IL; IN; KS; KY; MI; MO; MS; NE; OH; OK; TN; TX; WI; ON
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; FL; GA; NC; SC; West Indies (Cuba); Central America (Belize)
[WildflowerSearch map]
[BONAP county map]
Discussion

Hypericum sphaerocarpum differs from H. cistifolium and H. nudiflorum in its semiherbaceous habit and more northwestern distribution, as well as in its combination of relatively long, narrow leaves, persistent sepals, globose and apiculate to rounded capsules, and relatively large seeds. The narrow-leaved, bushy form from eastern parts of the range (var. turgidum) merges with the typical form.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Subspecies 3 (2 in the flora).

The two subspecies of Hypericum nitidum present in North America apparently remain distinct there; the distinctions are less clear in Cuba, where subsp. cubense (Turczaninow) N. Robson is also present.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Plants to 45+ dm, with ± numerous, stout, bushy-branched stems from base; leaf blade margins loosely inrolled, apex obtuse to rounded-apiculate; sepal apices shortly apiculate to acute.
subsp. nitidum
1. Plants 3–10 dm, with ± few, slender, little-branched stems from base; leaf blade margins tightly inrolled, apex acute to long-acuminate; sepal apices acute to long-acuminate.
subsp. exile
Source FNA vol. 6, p. 83. FNA vol. 6, p. 79.
Parent taxa Hypericaceae > Hypericum > sect. Myriandra Hypericaceae > Hypericum > sect. Myriandra
Sibling taxa
H. adpressum, H. anagalloides, H. apocynifolium, H. ascyron, H. boreale, H. brachyphyllum, H. buckleyi, H. canadense, H. canariense, H. chapmanii, H. cistifolium, H. concinnum, H. crux-andreae, H. cumulicola, H. densiflorum, H. denticulatum, H. dolabriforme, H. drummondii, H. edisonianum, H. ellipticum, H. erythreae, H. fasciculatum, H. frondosum, H. galioides, H. gentianoides, H. graveolens, H. gymnanthum, H. harperi, H. hypericoides, H. kalmianum, H. lissophloeus, H. lloydii, H. lobocarpum, H. maculatum, H. majus, H. microsepalum, H. mutilum, H. myrtifolium, H. nitidum, H. nudiflorum, H. paucifolium, H. perforatum, H. prolificum, H. pseudomaculatum, H. punctatum, H. radfordiorum, H. scouleri, H. setosum, H. suffruticosum, H. tenuifolium, H. tetrapetalum, H. virgatum, H. ×mitchellianum
H. adpressum, H. anagalloides, H. apocynifolium, H. ascyron, H. boreale, H. brachyphyllum, H. buckleyi, H. canadense, H. canariense, H. chapmanii, H. cistifolium, H. concinnum, H. crux-andreae, H. cumulicola, H. densiflorum, H. denticulatum, H. dolabriforme, H. drummondii, H. edisonianum, H. ellipticum, H. erythreae, H. fasciculatum, H. frondosum, H. galioides, H. gentianoides, H. graveolens, H. gymnanthum, H. harperi, H. hypericoides, H. kalmianum, H. lissophloeus, H. lloydii, H. lobocarpum, H. maculatum, H. majus, H. microsepalum, H. mutilum, H. myrtifolium, H. nudiflorum, H. paucifolium, H. perforatum, H. prolificum, H. pseudomaculatum, H. punctatum, H. radfordiorum, H. scouleri, H. setosum, H. sphaerocarpum, H. suffruticosum, H. tenuifolium, H. tetrapetalum, H. virgatum, H. ×mitchellianum
Subordinate taxa
H. nitidum subsp. exile, H. nitidum subsp. nitidum
Synonyms Brathydium chamaenerium, B. sphaerocarpum, H. chamaenerium, H. sphaerocarpum var. turgidum, H. turgidum Myriandra nitida
Name authority Michaux: Fl. Bor.-Amer. 2: 78. (1803) Lamarck: in J. Lamarck et al., Encycl. 4: 160. (1797)
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