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Viscum album
L.
Standardized Common
Name: European Mistletoe
Other Common Names: All-heal, Mistletoe
Family: Viscaceae or
Loranthaceae
Taxonomy: This genus includes
about 100 species, most found in Africa, Madagascar, and Asia. It is notable
for parasitism. Viscum album occurs from Europe to West Asia, and is the
more common of two European species. Subspecies are distinguished by host
preference. Viscum album subsp. album, which is often incorrectly
called subsp. platyspermum Kell., grows on flowering, hardwood trees and
is the subspecies most commonly harvested. Viscum album subsp. abietis
(Wiesb.) Abrom. and V. album subsp. austriacum (Wiesb.) Vollmann
grow on coniferous trees; these two subspecies were formerly segregated as V.
laxum Boiss. & Reuter. A yellow- or red-fruited Japanese variety, var. coloratum
(Kom.) Ohwi, also exists. Chemical composition may be influenced by the host
plant.
Description: Parasitic evergreen
perennial, rootless and attached to woody plants with tendrils that grow into
the tissue of the host plant (haustoria). Stems dichotomously branching, the
whole plant forming a spherical shape; internodes to 8(–10) cm long, dark or
yellowish green; buds covered by 2 bud scales, new shoots sometimes subtended
by 2 complementary shoots arising from axillae of bud scales. Leaves opposite
or occasionally whorled, (2–)3.5–6(–8) cm long and 1–2(–3) cm broad (or
narrower in subsp. austriacum), obovate to oblong or narrowly
lanceolate, coriaceous, yellowish green; base tapering; apex rounded; margins
entire; venation parallel with 3–7 main veins. Plants dioecious. Inflorescences
terminal, short-peduncled, 1–few-flowered, the flowers small and sessile. Male
flowers without calyx, 4-petaled, <4 mm in diameter; anthers numerous,
embedded in the thickened petals and shedding pollen from pores. Female flowers
ca. 1 mm in diameter, with calyx of 4 minuscule teeth, 4-petaled; ovary
inferior, lacking distinct ovules. Fruit a berry, usually white, sometimes
yellow or rarely red, 6–10 mm long, spherical to pear-shaped, containing 1
pseudoseed (rarely 2), each pseudoseed containing 1–3 embryos, surrounded by a
sticky viscous layer.
Parts
in Commerce:
Leafy shoots, usually collected before fruits have developed, sometimes with
fruits
Identification:
Stems
- Stems
dichotomously branching; internodes up to 8(–10) cm long and 4(–7) mm
thick, round or slightly flattened in cross-section
- Brittle, easily breaking
at nodes
- Surface
glabrous, longitudinally striated, yellowish green to dark green
- In
cross-section, stem has thin darker cortex, whitish inner portion
Leaves
- Leaf attachment
opposite or rarely whorled
- Leaves
(2–)3.5–6(–8) cm long and 1–2(–3) cm broad, obovate to oblong or
oblanceolate (longest and proportionally narrowest in subsp. abietis)
- Apex broader
than base, obtuse to rounded
- Base tapering to
short petiole
- Margins entire
- Blade thick and
leathery, hairless, yellowish green to dark green
- Primary venation
of 3(–7) parallel veins; if main veins >3, usually with 3 more
prominent than the others; veins more visible on underside, especially in
older leaves
- Odor faint,
peculiar
- Taste bitter,
peculiar
Flowers
and fruits
- Inflorescences
unisexual, few-flowered; flowers of both sexes tiny and inconspicuous
- Male flowers
2–3(–4) mm across, with 4 petals, numerous anthers completely sunken into
petals; pollen shedding from pores on petals
- Female flowers
1–1.5 mm across
- Fruit a berry,
6–10 mm long, round or somewhat pear-shaped, containing mucilaginous
substance in mesocarp and 1 pseudoseed (rarely 2)
- Fruit white
(yellowish in subsp. austriacum); unripe fruits green
- Taste of berries
somewhat sweet and bitter
The
three European subspecies may be distinguished by a combination of the
following characters:
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subsp. alba
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subsp. abietis
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subsp. austriacum
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Host
plants
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Hardwoods
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Firs (abies)
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Pines (Pinus) and larches (Larix).
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Leaf
shape
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Obovate to oblong, length usually <3X breadth, but highly variable
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Narrowly elliptical to lanceolate, oblong, ovate or obovate
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Lanceolate, length 4-6X breadth
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Leaf
and stem color
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Obtuse usually toothed all the way around and shallowly recurved
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Obtuse to rounded-truncate, with a visible gland
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Yellowish green
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Mature
fruit shape
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Shallow, irregular, usually pointed, serrate to dentate
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Very shallow, usually blunt, crenate to serrate
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Nearly round
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Phoradendron leucarpum
(Raf.) Reveal & M. C. Johnst.: Viscum album, which almost never
occurs in North America, must not be confused with American Mistletoe, P.
leucarpum (also known as P. serotinum (Raf.) M. C. Johnst.), which
is commercially valuable in its own right. Features of P. leucarpum that
distinguish it from V. album include:
- Stems slender,
woody, <3 mm thick, with internodes 1.5–3.5(–5) cm long, glabrous or
nearly so
- Leaves 1.5–4(–5)
cm long, broadly obovate to nearly round, with parallel veins from base
similar to V. album
- Leaves sessile
or with petioles 2–4 mm long, bases tapering to almost truncate
- Both male and
female inflorescences short, jointed spikes of 2 or more segments, each
segment bearing several to numerous tiny flowers sunken into the rachis
- Flowers of both
sexes with 3(–5) calyx lobes
- Anthers 3(–5),
sessile, borne at base of calyx lobes
The
fruits of P. leucarpum (which are white, round and 4–6 mm in diameter,
and form viscin threads) are commonly thought to be much more toxic than the
leaves; although this belief has been proven to be exaggerated, fruits should
be excluded from commercial material.
Adulterants: “Mistletoe” may
refer to a variety of parasitic plants in Viscaceae and the related family
Loranthaceae. The only other European species that might be confused with V.
album is Loranthus europaeus Jacq., which has brown stems, typically
pinnate leaf venation, yellow fruits, and male flowers with calyx teeth and
with stamens that are not sunk into the petals.
Teucrium chamaedrys L.
(Germander), which belongs to the mint family, is said by one source to have
been substituted for mistletoe. Germander is a non-parasitic subshrub with
hairy, somewhat quadrangular stems and leaves that are <2 cm long, broadly
ovate, usually hairy on the underside and often with toothed margins. Its flowers
are purple and 1–1.5 cm long; the corolla is hairy and bilaterally symmetrical,
with the upper lip missing. This plant should not readily be mistaken for
mistletoe.
References:
Becker H. European mistletoe: taxonomy, host trees,
parts used, physiology. In: Büssing A, ed. Mistletoe: the Genus Viscum.
Amsterdam: Harwood Academic Publishers; 2000:31–43. Medicinal and Aromatic
Plants—Industrial Profiles, vol. 16.
Grazi G, Urech K. Einige morphologische Merkmale der
Mistelbeere (Viscum album L.) und deren taxonomische Bedeutung. Beitr
Biol Pflanzen. 1981;56:293–306.
Heywood VH, Edmondson JR, eds. Loranthaceae. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. 2nd ed., vol. 1. Cambridge:
Cambridge University Press; 1993:86–87.
Ramm H, Urech K, Scheibler M, Grazi G. Cultivation
and development of Viscum album L. In: Büssing A, ed. Mistletoe: the
Genus Viscum. Amsterdam: Harwood Academic Publishers; 2000:75–94. Medicinal
and Aromatic Plants—Industrial Profiles, vol. 16.
Reveal JL, Johnston MC. A new combination in Phoradendron
(Viscaceae). Taxon. 1989;38:107–108.
Tutin TG, Wood D. Teucrium. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. Vol. 3. Cambridge: Cambridge University
Press; 1972:129–135.
Wiens D. Revision of the acataphyllous species of Phoradendron.
Brittonia. 1964;16:11–54.
Figure 82: a–b, Viscum album subsp. album habit with female inflorescence and male inflorescence.
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