''Laburnum'', sometimes called golden chain or golden rain, is a genus of two species of small

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

s in the subfamily

Faboideae The Faboideae are a subfamily of the flowering plant family Fabaceae or Leguminosae. An acceptable alternative name for the subfamily is Papilionoideae, or Papilionaceae when this group of plants is treated as a family. This subfamily is widely ...

of the pea family

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

. The species are '' Laburnum anagyroides''—common laburnum and '' Laburnum alpinum''—alpine laburnum. They are native to the mountains of southern

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

from

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

to the

Balkans The Balkans ( , ), corresponding partially with the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throug ...

. Some botanists include a third species, ''Laburnum caramanicum'', but this native of southeast Europe and

Anatolia Anatolia (), also known as Asia Minor, is a peninsula in West Asia that makes up the majority of the land area of Turkey. It is the westernmost protrusion of Asia and is geographically bounded by the Mediterranean Sea to the south, the Aegean ...

is usually treated in a distinct genus '' Podocytisus'', more closely allied to the ''

Genisteae Genisteae is a tribe of trees, shrubs and herbaceous plants in the subfamily Faboideae of the family Fabaceae. It includes a number of well-known plants including broom, lupine (lupin), gorse and laburnum. The tribe's greatest diversity is ...

'' (brooms).

Description

The ''Laburnum'' trees are

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

. The leaves are trifoliate, somewhat like a

clover Clovers, also called trefoils, are plants of the genus ''Trifolium'' (), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with the highest diversit ...

; the leaflets are typically long in ''L. anagyroides'' and long in ''L. alpinum''. They have yellow pea-

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s in pendulous leafless

raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...

s long in spring, which makes them very popular garden trees. In ''L. anagyroides'', the racemes are long, with densely packed flowers; in ''L. alpinum'' the racemes are long, but with the flowers sparsely along the raceme. The fruit develops as a pod and is extremely poisonous. The yellow flowers are responsible for the old poetic name 'golden chain tree' (also written as golden chaintree or goldenchain tree). All parts of the plant are

poison A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figurati ...

ous, although mortality is very rare. Symptoms of laburnum poisoning may include intense sleepiness, vomiting, convulsive movements, coma, slight frothing at the mouth and unequally dilated pupils. In some cases, diarrhea is very severe, and at times the convulsions are markedly tetanic. The main toxin in the plant is cytisine, a nicotinic receptor

agonist An agonist is a chemical that activates a Receptor (biochemistry), receptor to produce a biological response. Receptors are Cell (biology), cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an R ...

. It is used as a food plant by the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e of some

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

species, including the

Palearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

moth, the buff-tip.

Species

Accepted binomials

''Laburnum'' comprises the following species: * '' Laburnum alpinum'' (Mill.) Bercht. & J. Presl * '' Laburnum anagyroides'' Medik.

Species names with uncertain taxonomic status

The status of the following species is unresolved: * ''Laburnum album'' J.Presl * ''Laburnum arboreum'' J.Presl * ''Laburnum biflorum'' G.Nicholson * ''Laburnum fragrans'' Griseb. * ''Laburnum grandiflorum'' (DC.) J.Presl * ''Laburnum heuffelii'' Wierzb. ex Fuss * ''Laburnum ianigerum'' J. Presl * ''Laburnum intermedium'' Dippel * ''Laburnum jacquinianum'' Dalla Torre & Sarnth. * ''Laburnum jaquinianum'' Dieck * ''Laburnum laburnum'' (L.) Voss * ''Laburnum laburnum'' Dörfl. * ''Laburnum lanigerum'' J.Presl * ''Laburnum linneanum'' Dieck * ''Laburnum monadelphum'' Pritz. * ''Laburnum nigricans'' J.Presl * ''Laburnum nigricanum'' Fuss * ''Laburnum nubigenum'' J.Presl * ''Laburnum patens'' J.Presl * ''Laburnum pendulum'' Raf. * ''Laburnum praecox'' Fuss * ''Laburnum purpurascens'' hort. & Vilm. * ''Laburnum purpureum'' (Scop.) Drapiez * ''Laburnum ramentaceum'' (Sieber) K.Koch * ''Laburnum rochelii'' Wierzb. ex Fuss * ''Laburnum serotinum'' Hort. ex Dippel * ''Laburnum sessilifolium'' J.Presl * ''Laburnum spinosum'' J.Presl * ''Laburnum tardiflorum'' auct. * ''Laburnum triflorum'' J.Presl * ''Laburnum variabile'' hort. & Vilm. * ''Laburnum weldeni'' Griseb. ex Lavall. * ''Laburnum weldenii'' Griseb. ex Lavallée

Hybrids

The following hybrids have been described: * ''Laburnum'' × ''watereri'' (Wettst.) Dippel (''L. alpinum'' × ''L. anagyroides'') There is also a graft-chimaera, + ''Laburnocytisus'' 'Adamii' Lavallée.

Uses

Woodworking

''Laburnum'' has historically been used for cabinetmaking and inlay, as well as for musical instruments. In addition to such wind instruments as recorders and

flutes The flute is a member of a family of musical instruments in the woodwind group. Like all woodwinds, flutes are aerophones, producing sound with a vibrating column of air. Flutes produce sound when the player's air flows across an opening. In th ...

, it was a popular wood for

Great Highland Bagpipe The great Highland bagpipe ( 'the great pipe') is a type of bagpipe native to Scotland, and the Scottish analogue to the great Irish warpipes. It has acquired widespread recognition through its usage in the British Armed Forces, British mili ...

s before taste turned to imported dense tropical hardwoods such as '' Brya ebenus'' (cocus wood),

ebony Ebony is a dense black/brown hardwood, coming from several species in the genus '' Diospyros'', which also includes the persimmon tree. A few ''Diospyros'' species, such as macassar and mun ebony, are dense enough to sink in water. Ebony is fin ...

, and '' Dalbergia melanoxylon'' (African monkeywood). The heart-wood of a laburnum may be used as a substitute for ebony or rosewood. It is very hard and a dark chocolate brown, with a butter-yellow sapwood. Freshly cross cut Laburnum with heart-wood

Cultivation

''Laburnum''

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

and hybrids are cultivated as

ornamental trees Ornamental plants or ''garden plants'' are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars th ...

for gardens and parks. They are also trained as

espalier Espalier ( or ) is the horticulture, horticultural and ancient Agriculture, agricultural practice of controlling woody plant growth for the production of fruit, by pruning and tying branches to a frame. Plants are frequently shaped in formal patt ...

s on

pergola A pergola is most commonly used as an outdoor garden feature forming a shaded walkway, passageway, or sitting area of vertical posts or pillars that usually support crossbeams and a sturdy open lattice, often upon which woody vines are t ...

s, for ceilings of pendant flowers in season. In its natural form, ''Laburnum'' is a shrubby, multi-branched tree, but it is often pruned to maintain a single trunk which displays the smooth green bark. Gardeners are advised to remove the spent seedpods after flowering because they sap the strength of the tree and are the most poisonous part. Generally ''Laburnum'' does not perform well in hot climates, and has a reduced life-span if grown in climates with warm winters. Afternoon shade and the occasional deep watering are advisable in areas with hot, dry summers. They do best in climates with moderate winter and summer temperatures, ideally Oceanic climates like those of the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

and

Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other ge ...

. ''Laburnum'' trees are ubiquitous in

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

and

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

, where they are commonly planted as lawn specimens or in shrub borders. Most garden specimens are of the hybrid between the two species, ''Laburnum'' ×''watereri'' 'Vossii' (Voss's laburnum), which combines the longer racemes of ''L. alpinum'' with the denser flowers of ''L. anagyroides''; it also has the benefit of low seed production. It has gained the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...

Award of Garden Merit The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. It includes the full range of cultivated p ...

References

External links

Flora Europaea: ''Laburnum''

ILDIS Legume Database
* — ''time lapse of a year in the life of a Laburnum tree''.

{{Taxonbar, from=Q147184 Genisteae Fabaceae genera Trees of Europe Flora of Europe Flora of Italy Garden plants of Europe Ornamental trees