laburnum
{{Short description|Genus of plants}}
{{Other uses}}
{{Use dmy dates|date=July 2020}}
{{Automatic taxobox
| image = Laburnum_anagyroides2.jpg
| image_caption = Common laburnum – flowers
| taxon = Laburnum
| authority = Fabr.
| subdivision_ranks = Species
| subdivision = See text
}}
Laburnum, sometimes called golden chain or golden rain, is a genus of two species of small trees in the subfamily Faboideae of the pea family Fabaceae. The species are Laburnum anagyroides—common laburnum and Laburnum alpinum—alpine laburnum. They are native to the mountains of southern Europe from France to the Balkans.
Some botanists include a third species, Laburnum caramanicum, but this native of southeast Europe and Anatolia is usually treated in a distinct genus Podocytisus, more closely allied to the Genisteae (brooms).
Description
The Laburnum trees are deciduous. The leaves are trifoliate, somewhat like a clover; the leaflets are typically {{convert|2|–|3|cm|in|1|round=0.5|abbr=on}} long in L. anagyroides and {{convert|4|–|5|cm|in|round=0.5|abbr=on}} long in L. alpinum.
They have yellow pea-flowers in pendulous leafless racemes {{convert|10|–|40|cm|in|round=0.5|abbr=on}} long in spring, which makes them very popular garden trees. In L. anagyroides, the racemes are {{convert|10|–|20|cm|in|round=0.5|abbr=on}} long, with densely packed flowers; in L. alpinum the racemes are {{convert|20|–|30|cm|in|round=0.5|abbr=on}} long, but with the flowers sparsely along the raceme.Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press. {{ISBN|978-185918-4783}} The fruit develops as a pod and is extremely poisonous.Kilbracken, J. 1989. Easy way guide Trees. Larousse. {{ISBN|0-7523-0027-X}}
The yellow flowers are responsible for the old poetic name 'golden chain tree' (also written as golden chaintree or goldenchain tree).
Image:Laburnum anagyroides flowering.jpg
All parts of the plant are poisonous, although mortality is very rare.{{cite journal | author = Forrester R.M. | title = Have you Eaten Laburnum? | year = 1979 | journal = The Lancet| volume = 313 | issue = 8125 | pages = 1073 | doi = 10.1016/S0140-6736(79)92963-5 | pmid = 86787 | s2cid = 38961471 }} 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.
It is used as a food plant by the larvae of some Lepidoptera species, including the Palearctic moth, the buff-tip.
Species
=Accepted binomials=
Laburnum comprises the following species:{{cite web | url = http://www.ildis.org/LegumeWeb?version~10.01&genus~Laburnum&species~ | title = ILDIS LegumeWeb entry for Laburnum | author = | website = International Legume Database & Information Service | publisher = Cardiff School of Computer Science & Informatics | accessdate = 11 April 2014 }}{{cite web | url = http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?6427 | title = GRIN species records of Laburnum | author = USDA | author-link = USDA | author2 = ARS | author2-link = Agricultural Research Service | author3 = National Genetic Resources Program | website = Germplasm Resources Information Network—(GRIN) [Online Database] | publisher = National Germplasm Resources Laboratory, Beltsville, Maryland | accessdate = 11 April 2014 | url-status = dead | archiveurl = https://web.archive.org/web/20150924122101/http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?6427 | archivedate = 24 September 2015}}{{cite web | url = http://www.theplantlist.org/1.1/browse/A/Leguminosae/Laburnum/ | title = The Plant List entry for Laburnum | date = 2013 | website = The Plant List | publisher = Royal Botanic Gardens, Kew and the Missouri Botanical Garden | accessdate = 11 April 2014 }}
- Laburnum alpinum (Mill.) Bercht. & J. Presl
- Laburnum anagyroides Medik.
=Species names with uncertain taxonomic status=
The status of the following species is unresolved:
{{div col|colwidth=300px}}
- 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
{{div col end}}
=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, it was a popular wood for Great Highland Bagpipes{{cite book | author = Rendle BJ | title = World Timbers: Europe and Africa | volume = 1 | url = https://books.google.com/books?id=JIhGAAAAYAAJ| year = 1969 | publisher = Univ of Toronto Press | page = 40 | isbn = 978-0802015709 }} before taste turned to imported dense tropical hardwoods such as Brya ebenus (cocus wood), ebony, and Dalbergia melanoxylon (African monkeywood).{{cite book | author = Dickson J. | title = The Highland bagpipe: music, history, tradition | url = https://books.google.com/books?id=JOfk2YpundEC&pg=PA50|year=2009| publisher = Ashgate Publishing, Ltd. | isbn = 978-0-7546-6669-1 | page = 50 }} 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. File:Freshly cross cut Laburnum with heart-wood.jpg
=Cultivation=
Laburnum species and hybrids are cultivated as ornamental trees for gardens and parks. They are also trained as espaliers on pergolas, 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.{{cite book| title=Sunset Western Garden Book | editor=Kathleen Norris Brenzel | year=2007 | page=429 }} 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 and Northern Europe.{{cite web | url = http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=c115| title=Laburnum x watereri 'Vossii'|publisher=Missouribotanicalgarden.com| access-date=18 December 2017}} Laburnum trees are ubiquitous in England, Wales, Scotland and Ireland, 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's Award of Garden Merit.{{cite web | title = Plant Selector—Laburnum ×watereri 'Vossii' | url = http://apps.rhs.org.uk/plantselector/plant?plantid=1105 | publisher = Royal Horticultural Society | accessdate = 20 May 2013 | archive-date = 13 April 2014 | archive-url = https://web.archive.org/web/20140413150139/http://apps.rhs.org.uk/plantselector/plant?plantid=1105 | url-status = dead }}{{cite web | url= https://www.rhs.org.uk/plants/pdfs/agm-lists/agm-ornamentals.pdf | title = AGM Plants - Ornamental | date = July 2017 | page = 57 | publisher = Royal Horticultural Society | accessdate = 17 March 2018}}
References
{{Reflist}}
External links
- [http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Laburnum&SPECIES_XREF=&TAXON_NAME_XREF=&RANK= Flora Europaea: Laburnum]
- [https://web.archive.org/web/20140517100307/http://ildis.org/ ILDIS Legume Database]
- {{usurped|1=[https://web.archive.org/web/20040925221835/http://www.haworth-village.org.uk/nature/time-lapse/time-lapse.asp?pic=16 Laburnum tree video]}} — time lapse of a year in the life of a Laburnum tree.
- [http://www.botanical.com/botanical/mgmh/l/labrun02.html Grieve, 'A Modern Herbal' (1931)]
{{Commons category-inline|Laburnum}}
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