Hypericum perforatum L.
Standardized Common
Name: St.
John’s Wort
Other Common Name: Klamath Weed
Family: Hypericaceae or
Clusiaceae (Guttiferae)
Taxonomy: Hypericum is a widespread and
very diverse genus of about 450 species, divided into about 30 sections and
ranging from herbaceous weeds to large trees. H. perforatum is the type species of Sect. Hypericum, which includes 52 herbaceous species. The species is
native to Eurasia, where it may have originated through hybridization between H. maculatum Crantz and H. attenuatum Choisy. The best taxonomic
treatment recognizes four subspecies of H. perforatum, of which only
subsp. perforatum (Europe and North
America) and subsp. veronense
(Schrank) H. Lindb. (Europe and Southwest Asia) are widely distributed.
Considerable intergradation exists between these subspecies in Europe.
Description: Perennial herb;
stems (20–)30–70(–100) cm high, branching, clustered at base, tough, with 2
raised longitudinal ridges, bearing small dark glands. Leaves opposite, sessile
or subsessile, elliptic to linear-oblong, (5–)10–30(–35) mm long, 2–10 mm wide,
with translucent glandular dots; apices obtuse; margins entire. Inflorescences
cymose, leafy, many-flowered. Sepals narrowly lanceolate, 3–4 mm long,
glandular-punctate; apex acute to acuminate or attenuate. Petals orange-yellow,
obovate, 10–12 mm long, often slightly toothed at apical end on one side, with
black dots on the margin and occasional black streaks. Stamens numerous,
grouped in 3(–5) clusters, 6–8 mm long. Styles 3(–5); ovary of 3(–5) fused
carpels. Fruit a septicidal capsule, 6–8(–10) mm long, ovoid, with elongated
apex. Seeds numerous, brown to blackish, glossy, with netted ridges on surface.
Parts
in Commerce:
Whole herb
Identification:
Stem
- With 2 longitudinal lines, not with 4 lines or wings or round
- Hairless
- With few small black glandular dots on lines
Leaves
- Pale green
- Oblong to elliptical
or linear, mostly 10–30 mm long
- Secondary veins
curving to become parallel over most of leaf length, with inconspicuous
netted tertiary venation between
- Glands in blade
usually pale, conspicuous below; occasionally with a few black dots
- Hairless
- Petiole very
short or absent
- Leaf base
rounded to tapering, or cordate and somewhat clasping in one Asian
subspecies
- Margins entire,
often slightly revolute, with few small black glands near apex
Sepals
- 5, 3–4 mm long,
narrow
- Surface has
clear glandular spots; black dots or streaks absent or sparse
- Lacking
elongated oil vesicles
- Margins usually
entire, with no or few black glands
Petals
- 5, 10–12 mm
long, obovate
- Orange-yellow,
with darker veins
- Few black dots
near margin, sometimes with black dots or streaks or pale glands elsewhere
on surface
Stamens
- Numerous, borne
in 3 bundles (very rarely in 5)
- Filaments long,
narrow, yellowish
- Black glands
present on anthers
Adulterants: Several European
species of Hypericum have been found as adulterants. All of these, as
well as similar American species, can be distinguished morphologically.
Hybridization between H. maculatum and H. perforatum is known to
occur in eastern Europe, and a series of intermediates exists. H. maculatum
is characterized by:
- Stem lines 4
- Leaves with few
or no clear glandular dots
- Leaf veins
conspicuously netted
- Sepals broader
and somewhat toothed
- Petals with few
black dots along the margins but with numerous black dots and streaks
elsewhere on the surface
First-generation
hybrids are intermediate in form, often having 2 conspicuous and 2 weak lines
on the stem. Gene flow between the two species is probably uncommon but of
longstanding natural occurrence.
References:
Mártonfi P, Repčak M, Mihoková L. Hypericum
maculatum Crantz subsp. maculatum ×H. perforatum L. (Hypericaceae):
Corroboration of natural hybridization by secondary metabolite analysis. Folia
Geobot Phytotax. 1996;31:245–250.
Robson NKB. Hypericum. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. Vol. 2. Cambridge: Cambridge University
Press; 1968:261–269.
Robson NKB. Studies in the genus Hypericum L. (Guttiferae) 4(2). Section
9. Hypericum sensu lato (part 2):
subsection 1. Hypericum series 1. Hypericum. Bull Nat Hist Mus Lond
(Bot). 2002;32:61–123.
Robson NKB. Hypericum
botany. In: Ernst E, ed. Hypericum: the
Genus Hypericum. London: Taylor & Francis; 2003:1–22. Medicinal and Aromatic Plants—Industrial
Profiles, vol. 31.
Wichtl M, ed. Herbal Drugs and
Phytopharmaceuticals, 3rd English
ed. Stuttgart: medpharm Scientific Publishers and Boca Raton, FL: CRC Press;
2004:305–308.
Figure 33: Hypericum perforatum habit, flower and leaf.
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