Species of flowering plant
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Lamium galeobdolon, the yellow archangel, is a species of flowering plant in the mint family Lamiaceae. It is native to Europe and western Asia but it is widely introduced in North America and elsewhere. It is the only species in the genus "Lamium" with yellow flowers. Another common name for this species is golden dead-nettle. In New Zealand, it is called the aluminium plant or artillery plant. The common names archangel and dead-nettle have been in use for hundreds of years, dating back to at least the 16th century.
"Lamium galeobdolon" comprises four closely-related subspecies that are sometimes considered to be four separate species, one of which, the variegated yellow archangel ("Lamium galeobdolon" subsp. "argentatum") from central Europe, is widely present as an invasive subspecies in several European countries outside of its native range and also in New Zealand, Canada, and the United States.
Description.
"Lamium galeobdolon" "sensu lato" is a perennial plant with square stems growing from tall. The paired opposite leaves are stalked with toothed margins. The leaves are long, and may or may not have silvery markings (an important character used to distinguish subspecies). The inflorescence is a pseudo-whorl of 4–16 flowers (called a verticillaster) clustered around the axil of a leaf-pair. Each flower has bilateral (zygomorphic) symmetry. The calyx is five-lobed and the corolla is yellow with a prominent hood. The flower's lower lip has three lobes with the central lobe often streaked with orange. There are two short stamens and two long ones. Flowering is in late spring to early summer, typically May–June in Britain. A pair of fused carpels give rise to a four-chambered schizocarp.
Identification.
Subspecies of "Lamium galeobdolon" "sensu lato" are the only taxa in the genus with yellow flowers. All of the subspecies are stoloniferous except subspecies "flavidum". The invasive subspecies "argentatum" is readily distinguished by its silvery white variegated leaves. The two subspecies "galeobdolon" and "montanum" can be difficult to distinguish but assuming the plant in question is in full flower, subspecies "galeobdolon" has a maximum of six (rarely seven) flowers per verticillaster while subspecies "montanum" averages ten flowers per verticillaster. The hairiness of the lower stems is also a useful clue, with subspecies "galeobdolon" having hairs on the four ridges only, while subspecies "montanum" is more uniformly hairy across the faces as well as the ridges.
"Lamium galeobdolon" subsp. "flavidum" is notable for the lack of stolons, frequently branched fertile stems with upright flowering lateral shoots, and 10–16 small flowers per verticillaster. An identification key for the remaining taxa follows:
Other taxa in the group can have marked leaves but those of subsp. "argentatum" are distinctive:
 ;templatestyles src="Template:Blockquote/styles.css" / ;Permanent silvery pattern on leaf lamina in "L. argentatum" always forms two flexuous bands along the midrib, mostly not interrupted by the lateral veins. They are distinctive particularly from the late autumn to the early spring when a contrast brownish-maroon colouring develops on the abaxial side and extends to the midrib-zone of the upper leaf side. Although variegated leaves were frequently observed in all other taxa in our study, they never matched the description above. Silvery-grey markings constituted merely separate splashes or flecks (small-sized in "L. montanum" and "L. flavidum", larger in "L. galeobdolon"), not merged into continuous bands. Thus, a combination of two distinct silvery flexuous bands together with a strong chocolate-maroon zone along the midrib in winter can be regarded as specific "L. argentatum" markers.
In particular, a cultivar of subspecies "flavidum" known as 'Herman's Pride' has silver-spotted leaves, but even though the markings are unlike those of subspecies "argentatum", the two taxa are sometimes confused.
The base chromosome number of taxa in genus "Lamium" is x = 9. "Lamium galeobdolon" subsp. "flavidum" and subsp. "galeobdolon" are diploid (2n = 2x = 18) while subsp. "argentatum" and subsp. "montanum" are tetraploid (2n = 4x = 36). A few triploid individuals have been reported. The triploids are thought to be natural hybrids between diploid subsp. "galeobdolon" and tetraploid subsp. "argentatum".
Taxonomy.
"Lamium galeobdolon" was first described as "Galeopsis galeobdolon" by Carl Linnaeus in 1753. Linnaeus himself transferred the species to genus "Lamium" in 1759, and therefore the correct name in "Lamium" is "Lamium galeobdolon" (L.) L. The latter has six homotypic synonyms, one of which, "Lamiastrum galeobdolon" (L.) Ehrend. &amp; Polatschek, is widely used.
The name "galeobdolon" (or "Galeobdolon") has a long history. It was used by Pliny the Elder in the first century AD. Johann Jacob Dillenius referred to genus "Galeobdolon" in 1719, followed by Michel Adanson (1763), William Hudson (1778), and dozens of others. George Bentham used "Galeobdolon" as the name of a section in 1848. Later, in 1864, Paul Friedrich August Ascherson used it as the name of a subgenus. From the time of Linnaeus, numerous authors have used the specific epithet "galeobdolon" in the names of species. Altogether there are dozens of botanical names that use "galeobdolon" (or "Galeobdolon") at least once. Most of them are synonyms for just a few taxa.
Most authorities with a global scope accept four closely-related taxa, either as subspecies of "Lamium galeobdolon" (L.) L. or as full species in "Lamium" L. Other authorities accept one or more taxa in "Lamiastrum" Heist. ex Fabr. or "Galeobdolon" Huds.
"Lamium galeobdolon" subsp. "argentatum" was first described as "Galeobdolon argentatum" by Miroslav Smejkal in 1975. In a comprehensive and influential treatment of genus "Lamium" published in 1989, Jacob Mennema reduced the species to forma and placed it in synonymy with "Lamium galeobdolon" subsp. "galeobdolon". Hence subsp. "argentatum" was neglected for a long time and its invasion history is poorly documented.
Based on nuclear DNA data, "Lamium" is monophyletic whether "L. galeobdolon" "sensu lato" is included or not. Based on chloroplast DNA data, however, the same study found "Lamium" to be paraphyletic if "L. galeobdolon" is segregated to genus "Lamiastrum". Subsequent studies have found "Lamiastrum" to be nested within "Lamium", that is, a separate genus is not warranted. The recognition of full species in "Lamium" is likewise not supported by molecular analysis.
Etymology.
Both the generic name "Lamium" and the specific epithet "galeobdolon" were used by Pliny the Elder in the first century AD. The name "galeobdolon" has several possible origins. It may come from the Latin words "galeo" meaning "to cover with a helmet" and "dolon" meaning "a fly's sting", or it may come from the Greek words "galen" meaning "weasel" and "bdolos" meaning "foetid smell". The latter interpretation is likely the source of the old common name 'yellow weasel-snout'.
The common names archangel and dead-nettle have been in use for hundreds of years. In 1578 Rembert Dodoens observed that "Dead nettell groweth every where". John Gerard used the word "archangel" in 1633. Gerard believed the dead-nettles were so-named because their leaves resembled those of the true nettles in the family Urticaceae. The names "Arch-Angel" and "Dead Nettle" appear in the book "The English Physitian" (also known as the "Complete Herbal") published by the English botanist and herbalist Nicholas Culpeper in 1652. Both Dodoens and Gerard believed the name "archangel" referred to members of genus "Lamium" with "clusters of hooded flowers at the nodes rising along the stems like a choir of robed figures". Others believe the name refers to the wing-like shape of its paired opposite leaves.
Distribution.
"Lamium galeobdolon" "sensu lato" is native across Europe, western Asia, and portions of the Middle East. It ranges from Ireland and Spain eastward across Europe as far as the West Siberian Plain and southeastward to Iran. Subspecies "flavidum" is native to the Alps, northern Italy, and the mountain ranges northeast of the Adriatic Sea. The two subspecies "galeobdolon" and "montanum" have broadly similar distributions, but the latter extends further west and south than subspecies "galeobdolon", which itself has a more northeast distribution. Within Britain and Ireland, subspecies "montanum" is widespread across England and Wales and locally in southern Scotland and eastern Ireland, while subspecies "galeobdolon" is restricted to a small area in Lincolnshire in eastern England.
"Lamium galeobdolon" "sensu lato" is widely introduced in several European countries outside of its native range, and also in New Zealand, Canada, and the United States, but authorities disagree about the distribution of introduced subspecies. As of April 2024[ [update]], Plants of the World Online (POWO) claims that subspecies "argentatum" has been introduced in Great Britain, Ireland, and Italy, but since it is elsewhere reported to be introduced in the Netherlands and Switzerland, the list is incomplete. POWO also claims that subspecies "galeobdolon" has been introduced in Madeira, New Zealand (both North Island and South Island), and the United States, but iNaturalist data show that subspecies "argentatum" is the most widespread subspecies in all of these areas. Since authoritative sources based in North America implicitly refer to "Lamium galeobdolon" "sensu lato", POWO's claim is unsubstantiated. The list of U.S. states where "Lamium galeobdolon" "sensu lato" is said to occur varies dramatically depending on the source.
Ecology.
"Lamium galeobdolon" "sensu lato" has been widely introduced as a garden plant (often under the name "Lamiastrum galeobdolon"), especially in New Zealand, Canada, and the United States where it has escaped cultivation and become an invasive species. In New Zealand, it is listed by the 2020 National Pest Plant Accord and therefore banned from sale, propagation, and distribution throughout the country. It is also listed by the Invasive Species Council of British Columbia in Canada. In the U.S. state of Washington, it is listed as a Class B Noxious Weed and therefore banned from sale by state law. It is also a B-listed Noxious Weed in the state of Oregon.
The variegated yellow archangel ("Lamium galeobdolon" subsp. "argentatum") has become an invasive subspecies in several European countries. In the Netherlands, subspecies "argentatum" was introduced as an ornamental ground cover, and by 1985 it had become naturalised and recorded in more localities than the native subspecies "galeobdolon". It is also invasive in Britain where it spreads by stolons at the rate of per growing season. In western England, it is found far from human habitations, which suggests it did not originate from garden waste and must therefore be spreading by other means. In Switzerland, subspecies "argentatum" tripled its occurrence in four decades (1980–2020) while exhibiting "a higher growth rate and regeneration capacity" than the native subspecies "galeobdolon".
Outside of its native range, the invasive subspecies of "Lamium galeobdolon" in particular areas is largely unknown. In the Lower Mainland of British Columbia, the invasive entity is said to be a cultivar of subspecies "montanum" called 'variegatum' (also known as 'Florentinum'). A cultivar of subspecies "argentatum" called 'Florentinum' (also known as 'variegatum') has invaded the Seattle area in Washington State.
Based on morphological characters, number of chromosomes, pattern of geographical distribution, and phytochemistry, early botanists hypothesized that the tetraploid subsp. "montanum" originated as a hybrid between the two diploid taxa, subsp. "flavidum" and subsp. "galeobdolon". However, more recent phylogenetic data suggests that subsp. "montanum" originated from subsp. "flavidum" alone. Similarly, there is conflicting evidence regarding the origins of the tetraploid subsp. "argentatum" suggesting that it may or may not have originated from subsp. "galeobdolon" alone.
References.
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