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

fourpetal St. Johnswort

Habit Herbs (perennial) or subshrubs, erect or decumbent, not or rarely rhizomatous, unbranched or branched proximally, 2–6 dm. Herbs (perennial) or shrubs, erect, with woody base, usually unbranched, sometimes with divaricate or ascending branches, 2–10 dm.
Stems

internodes 2–4-lined.

internodes (2–)4-lined at first, then 2-lined to 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 oblong-ovate to ovate or triangular-ovate, 5–35 × 4–15 mm, base articulated, cordate-amplexicaul, margins subrecurved, apex apiculate or obtuse to rounded, midrib with 1 pair of branches.

Inflorescences

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

terminal, 1(–3)-flowered, branching from apical node pseudodichotomous, sometimes with relatively short branches from to 3 proximal nodes.

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.

20–30 mm diam.;

sepals persistent, enclosing capsule, 4, unequal, outer broadly ovate, 7–15 × 5.5–10 mm, apex subapiculate to obtuse, inner narrowly lanceolate, 7–15 × 2–3 mm, apex acute;

petals 4, bright yellow, obovate-oblong, 10–15 mm;

stamens persistent, 100;

ovary 3-merous.

Capsules

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

broadly ellipsoid-ovoid to subglobose, 5–6 × 3.5–4 mm.

Seeds

carinate, 2–2.7 mm;

testa coarsely reticulate.

not carinate, 0.7 mm;

testa shallowly scalariform.

2n

= 18.

Hypericum sphaerocarpum

Hypericum tetrapetalum

Phenology Flowering summer (Jun–Aug). Flowering winter–spring (Jan–Apr), late summer (Jul–Sep).
Habitat Rocky outcrops or embankments, prairies, stream banks, usually wet or moist, railroad embankments Moist, low pinelands, ditches
Elevation 500–1000 m (1600–3300 ft) 0–200 m (0–700 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; West Indies (w Cuba)
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[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.)

Hypericum tetrapetalum differs from H. crux-andreae in having broader leaves with strongly cordate-amplexicaul bases and, nearly always, by terminal pseudodichotomous inflorescences.

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

Source FNA vol. 6, p. 83. FNA vol. 6, p. 86.
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. nitidum, 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. virgatum, H. ×mitchellianum
Synonyms Brathydium chamaenerium, B. sphaerocarpum, H. chamaenerium, H. sphaerocarpum var. turgidum, H. turgidum Ascyrum amplexicaule, A. cubense, A. tetrapetalum
Name authority Michaux: Fl. Bor.-Amer. 2: 78. (1803) Lamarck: in J. Lamarck et al., Encycl. 4: 153. (1797)
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