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Urtica
dioica L. subsp. Dioica
Standardized Common
Name: Stinging Nettle
Other Common Names: Common Nettle,
Nettle
Family: Urticaceae
Taxonomy: Urtica
includes about 45 species of herbs with stinging hairs. Eleven species are
found in Europe and four in North America. Urtica dioica is divided into
three subspecies. Urtica dioica subsp. dioica, native to Eurasia
and naturalized in several areas of the United States, is, according to Herbs
of Commerce, the only material officially sold in the U.S. as Stinging Nettle.
The most widespread North American subspecies, subsp. gracilis (Aiton)
Selander, is sold as California Nettle because it was formerly treated as a
separate species, sometimes called U. californica Greene. It is not
always clearly distinguishable from the Western North American Urtical
dioica subsp. holosericea (Nutt.) Thorne.
Description: Dioecious,
rhizomatous perennial herb. Stems 0.3–1.5(–3) m high, sometimes weak and
sprawling, branched or unbranched, quadrangular, pubescent and bearing stinging
hairs. Leaves opposite, petiolate, stipulate, ovate to elliptical or
lanceolate, (1–)3–20 cm long; base rounded to cordate or rarely truncate; apex
acute to acuminate; margins serrate to biserrate; both surfaces normally
pubescent with stinging hairs, the lower surface usually also bearing
nonstinging hairs, especially over veins. Inflorescences paniculate, to 10 cm
long, bracteate, with numerous flowers borne in clusters. Flowers minute (<1
mm long), green, unisexual; tepals 4; male flowers with 4 stamens; female
flower with 1 ovary, 1-ovuled. Fruit an achene, 1.1–1.3 mm long.
Parts
in Commerce:
Leaves, or rhizome and roots
Identification: Characteristic
stinging hairs are normally present on aboveground vegetative parts. These can
be distinguished from other hairs by their larger size (often 1–2 mm long) and
their shape. The body of the hair is straight, sturdy and colorless. The base
of the hair is often distinct from the shaft, bulbous or slightly elongated,
and yellowish.
Leaves:
- Blade ovate to
lanceolate or elliptical, variable in size (2–14 cm)
- Petiole less
than half as long as blade, bearing stinging hairs
- Base cordate to
rounded or rarely truncate
- Apex acute to
acuminate
- Margins coarsely
serrate, rarely biserrate
- Upper surface
dark green, darker than lower
- Both surfaces
usually bearing stinging hairs (except in rare variants)
- Leaves usually
more or less pubescent with straight pale nonstinging hairs, at least
along veins of lower surface, sometimes on both surfaces; sometimes
glabrous
- Venation
pinnate; several secondary veins arising from base, the innermost pair
most prominent; major veins conspicuous beneath, often yellowish; ultimate
venation reticulated, observable beneath
- Stem fragments
quadrangular, with whitish pith, the smaller stems pubescent and bearing
stinging hairs
- Little odor or
taste
Urtica
dioica
subsp. gracilis (California Nettle) is very similar to subsp. dioica
in leaf morphology. Stinging hairs are only sparsely present on the stems and
leaves, and may be restricted to one leaf surface, whereas subsp. dioica
frequently has numerous stinging hairs on the stems and leaves. Literature
states that the lower surface will always bear most of the stinging hairs, but
some herbarium specimens have been observed to have most of the stinging hairs
on the upper surface. Otherwise, the leaves are glabrous or barely pubescent.
Urtica
urens
L. (Dwarf Nettle)
differs from typical U. dioica in several features:
- Leaves smaller,
the blades usually 1–3.5(–5) cm long
- Petiole variable
in length, sometimes as long as blade
- Petiole usually
lacks stinging hairs
- Blade elliptical
to suborbicular
- Base cuneate to
rounded-truncate
- Marginal teeth
deeply incised, often rounded
- Stinging hairs
mostly on upper surface of leaf
- Leaves otherwise
glabrous or barely pubescent with small fine hairs on upper surface
- Stem fragments
with few to many stinging hairs, otherwise glabrous
Rhizome
and roots
- Rhizome
yellowish-brown, 3–10 mm thick (most commonly 5–6 mm in dried material),
tapering, sometimes branching
- Roots arising at
swollen nodes of rhizome; larger roots 1–5 mm thick, often grayish;
rootlets numerous, very thin, tough
- Internodes 1–3
cm long, longitudinally furrowed
- Fracture
fibrous, tough
- Internodes
hollow; inner surface whitish
- Larger roots
longitudinally furrowed and twisted, often grayish; rootlets smooth
- Rhizome
cross-section shows thin cork and cortex; pericycle containing small
clusters of fibers and large crystals; distinct cambium; ring of narrow
rays of vascular tissue separated by broad rays of parenchyma that contain
bands of lignified cells; pith of simple parenchyma, broken down and
hollow in the center.
- Root
cross-section similar to rhizome, with secondary vascular tissue
containing broad parenchyma rays with bands of lignified cells; center of
root contains small amount of primary xylem rather than a hollow space
- Taste bitter
Adulterants: According to Wichtl,
U. kiovensis Rogow. (marsh nettle) and U. pilulifera L. (Roman
nettle) have rarely occured as adulterants of nettle root. Both have
essentially identical root anatomy, meaning that they could not be
distinguished morphologically, and the latter species is also chemically
identical. Substitution of other nettle species is probably not a significant
quality control problem.
The unrelated Lamium album L. (White
Nettle, Dead Nettle), which belongs to the mint family but strongly resembles
nettle, has been reported as an adulterant of nettle leaf. It can be
distinguished by its lack of stinging hairs on any part. Its leaves are usually
pubescent on both surfaces and ciliate on the margins; yellowish or dark
glandular spots may be seen on the lower surface. The marginal teeth are often
more rounded (crenate) than is typical of U. dioica.
References:
Ball PW, rev. Geltman DV. Urtica. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. 2nd ed., vol. 1. Cambridge:
Cambridge University Press; 1993:79–80.
Boufford DE. Urticaceae. In: Flora of North America
Editorial Committee, eds. Flora of North America, vol. 3. New York, NY:
Oxford University Press; 1997:400–413.
British Herbal Medicine
Association. British Herbal Pharmacopoeia. BHMA; 1996:143–144.
Corsi G, Garbari F, Maffei F. Il genere Urtica
L. (Urticaceae) in Italia. Revisione biosistematica. Webbia.
1999;53:193–239.
Wichtl M, ed. Herbal Drugs and
Phytopharmaceuticals, 3rd English
ed. Stuttgart: medpharm Scientific Publishers and Boca Raton, FL: CRC Press;
2004:617–625.
Woodland DW. Biosystematics of the perennial North
American taxa of Urtica. II. Taxonomy. Syst Bot. 1982;7:282–290.
World Health
Organization. WHO Monographs on Selected Medicinal Plants. Vol. 2. Geneva: World Health Organization;
1999–2002:329–341.
Figure 81: a, Urtica dioica leaf; b, Urtica urens leaf.
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