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dwarf st john's wort, millepertuis nain, small Canadian St. John's-wort

dwarf St. John's-wort, small Canadian St. John's-wort, small flower st john's wort

Habit Herbs annual or perennial, usually erect, sometimes decumbent and rooting, basal branches sometimes present, usually with to 10 pairs of spreading branches distal to middle, 0.5–8 dm.
Stems

apical internode shorter than adjacent one or almost absent.

internodes 4-angled.

Leaves

blades variable, rarely broadly ovate or suborbiculate.

spreading, sessile or amplexicaul;

blade paler abaxially, ovate, elliptic, or elliptic-oblong (proximal), ovate or suborbiculate to elliptic or lanceolate (mid and distal), 3–27(–40) × 1–15 mm, papery to membranous, margins plane, apex obtuse to rounded, basal veins 3–5, midrib with to 3 pairs of branches.

Inflorescences

branching from 2–10 nodes, mostly dichasial.

cylindric, 5–60-flowered, branching mostly dichasial;

bracts linear-subulate.

Flowers

3–5 mm diam.;

sepals lanceolate to linear-lanceolate or elliptic-oblong to oblanceolate, equal or unequal, 2–4.5 × 0.6–1.5 mm, margins sometimes ciliate, not setulose-ciliate, apex usually acute to apiculate, sometimes obtuse to rounded;

petals pale yellow, oblong, 1.7–3.5 mm;

stamens 5–16, scarcely grouped;

styles 0.5 mm;

stigmas broadly capitate.

Capsules

narrowly ovoid to cylindric-ellipsoid, 2–5 × 1.6–2.4 mm, usually broadest at or near middle.

Seeds

0.4–0.7 mm;

testa finely linear-scalariform.

Sepals

not imbricate or broader beyond middle or, if imbricate, leaves not broadly ovate to suborbiculate.

2n

= 16.

Hypericum mutilum subsp. mutilum

Hypericum mutilum

Phenology Flowering summer–fall (Jun–Oct).
Habitat Ditches, marshes, lake margins, desiccated temporary pools
Elevation 0–400 m (0–1300 ft)
Distribution
from FNA
AL; AR; CA; CO; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MO; MS; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; TN; TX; UT; VA; VT; WA; WI; WV; BC; NB; NS; ON; QC; SK [Widely introduced in Central America, South America, Europe, Pacific Islands (Hawaii, New Zealand)]
from FNA
AL; AR; CA; CO; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MO; MS; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SC; TN; TX; UT; VA; VT; WA; WI; WV; BC; NB; NS; ON; QC; SK [Introduced in w North America]
[WildflowerSearch map]
[BONAP county map]
Discussion

The records of subsp. mutilum from British Columbia and Saskatchewan and from California, Colorado, Oregon, and Utah (no details seen) are almost certainly all the result of introduction, as may be some other peripheral records.

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

Subspecies 2 (2 in the flora).

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

Key
1. Stems: apical internode shorter than adjacent one or almost absent; inflorescences: branching mostly dichasial from 2–10 nodes.
subsp. mutilum
1. Stems: apical internode usually longer than adjacent one; inflorescences: branching from 1–4(–6) nodes, branches diffuse and repeatedly monochasial distally.
subsp. latisepalum
Source FNA vol. 6, p. 94. FNA vol. 6, p. 93.
Parent taxa Hypericaceae > Hypericum > sect. Brathys > Hypericum mutilum Hypericaceae > Hypericum > sect. Brathys
Sibling taxa
H. mutilum subsp. latisepalum
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. 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. tetrapetalum, H. virgatum, H. ×mitchellianum
Subordinate taxa
H. mutilum subsp. latisepalum, H. mutilum subsp. mutilum
Synonyms Brathys euphorbioides, B. quinquenervia, H. euphorbioides, H. mutilum var. densiflorum, H. mutilum var. foliosissimum, H. mutilum var. minimum, H. mutilum var. parviflorum, H. quinquenervium Sarothra mutila
Name authority unknown Linnaeus: Sp. Pl. 2: 787. (1753)
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