Marrubium
vulgare L.
Standardized Common
Name: Horehound
Other Common Name: White Horehound
Family: Lamiaceae (Labiatae)
Taxonomy: Marrubium includes about 30 Eurasian and Mediterranean species; M.
vulgare is the most widely distributed.
Description: Perennial herb.
Stems to 45 cm high, weak, quadrangular, branched at the base with branches
ascending, pubescent with soft tangled white hairs. Leaves opposite, petiolate,
ovate or elliptic to orbicular or transversely elliptic, 1.5–5(–6) cm long,
1–4.5 cm broad; base narrowed, rounded, truncate, or subcordate; apex obtuse;
margin coarsely crenate; venation pinnate and reticulated, conspicuous; upper
surface rugose, somewhat pubescent to nearly subglabrous; lower surface densely
white-pubescent, with multicellular branched hairs and glandular hairs.
Inflorescences verticillate, axillary, globose, many-flowered; flowers
subtended by pubescent bracteoles. Calyx 5–7 mm long; tube 10-nerved,
10-toothed, pubescent; teeth narrow, equal, spreading, lower part hairy, tips
sharp-pointed and reflexed. Corolla white, bilabiate, longer than calyx,
typically 7–8 mm long, more or less pubescent; upper lip erect, notched; lower
lip spreading, 3-lobed, with middle lobe largest. Stamens 4, 2 longer, 2
shorter. Style gynobasic. Fruit 4 nutlets, triangular and blackish at maturity.
Parts
in Commerce:
Leaves and flowering tops
Identification:
Stem
and leaves
- Stem portions in
flowering tops with long, soft white hairs
- Leaves 1.5–5(–6)
cm long, broadly ovate to orbicular
- Leaf apex obtuse
- Margins coarsely
crenate
- Underside of
leaf with prominent venation, shortly woolly-pubescent especially on
veins, with multicellular stellate hairs and glandular hairs
- Upper surface of
leaf coarsely wrinkled, much less hairy than the lower, with conspicuous
netted venation
- Taste bitter
Flowers
- Bracteoles
subtending flowers narrow, pubescent, with awl-shaped tips
- Calyx narrowly
tubular, 10-toothed, usually ca. 5–7 mm long
- Calyx with dense
ring of long soft hairs at mouth; outer surface strongly tomentose,
especially on nerves
- Calyx teeth
narrow, of equal length, sharp-tipped, reflexed
- Corolla at least
slightly longer than calyx; white, or yellowed when dried, but not pink or
purple
- Lower lip of
corolla spreading, 3-lobed, with middle lobe widest; upper lip erect,
notched
Adulterants: Ballota hirsuta Benth., Ballota nigra L. (Black
Horehound), Marrubium peregrinum L. (also called Black Horehound), and M.
incanum Desr. are morphologically similar and are reported as adulterants
to M. vulgare. Each of these species has distinguishing features:
Ballota hirsuta
- Branched trichomes on leaves with longer basal stalks; sometimes
with gland at the tip of the central hair
- Calyx broadly funnelform, densely hairy, with 10 short, triangular
teeth
- Outside of upper lip of corolla extremely hairy
Ballota nigra
- Leaves variable, but often narrowly ovate, with acute apex; margins
often serrate rather than crenate; often not distinctly wrinkled
- Calyx funnelform rather than tubular; teeth only 5, triangular with
short awns
- Outside of upper lip of corolla extremely hairy; corolla may be
purplish
Marrubium incanum
- Leaves oblong to ovate, not approaching round; margins may be
shallowly dentate to serrate
- Calyx teeth only 5; teeth erect or spreading, but not recurved at
tip
Marrubium peregrinum
- Stem hairs short, appressed
- Leaves narrower than in M. vulgare
- Upper leaf surface densely woolly-pubescent
- Flowers in whorls of 10 or fewer; bracteoles short
- Calyx tube less hairy than in M. vulgare; teeth only 5, erect
to spreading
Marrubium ×paniculatum
Desr. (also known as M. remotum Kit.), a Central European hybrid
originating from a cross between M. peregrinum and M. vulgare, is
another reported contaminant. Like M. peregrinum, its upper leaf surface
is often densely woolly-pubescent. It has 8–10 calyx teeth, distinctly unequal
in size, with tips not more than slightly recurved.
References:
Cullen J. Marrubium. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. Vol. 3. Cambridge: Cambridge University
Press; 1972:137–138.
Marmey F. Contribution a l’étude morphologique et
anatomique du genre Marrubium L. au Maroc. Trav Inst Sci Chérif, sér
Bot. 1958;14:1–93 + plates.
Seybold S. Revision der persischen Marrubium-Arten
(Labiatae). Vorarbeiten zur Flora Iranica Nr. 20. Stuttgarter Beitr Naturk
Ser A (Biol). 1978;310:1–31. [Also OPTIMA Leaflet 72:1–31.]
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:740–748.
Figure 43: a, Marrubium vulgare inflorescence. b-c, M. vulgare flower and leaf; d, M. perigrinum leaf; e-f, Ballota hirsuta inflorescence and leaf; g-h, B. nigra inflorescence and leaf.