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Laburnum (ancient Latin name). Leguminosae. Including Podocytisus. Golden-chain. Ornamental trees or shrubs chiefly grown for their showy racemes of yellow flowers.
Deciduous: lvs. alternate, petioled, 3-foliolate, without stipules: fls. slender-pedicelled, in terminal simple racemes, mostly pendulous; calyx 2- lipped, with obtuse, short lips; corolla papilionaceous, with the petals all distinct; stamens 10, all connate; ovary stalked: fr. a linear pod with several seeds, compressed, tardily dehiscent; seed without appendage at base.—Three species in S. Eu. and W. Asia, often included under Cytisus. All parts of the plants are poisonous, especially the young frs. The hard, tough and closegrained wood is susceptible of a very fine polish, and is manufactured into various small articles.
The golden-chains are handsome small trees with dark green trifoliolate leaves falling late in autumn without change of color, and with drooping racemes of bright yellow flowers in late spring, followed by long narrow pods remaining on the tree a long time. They are adapted for planting on rocky slopes or in borders of shrubberies, where they should be allowed enough space to show to the best advantage their graceful, drooping racemes of golden flowers, which contrast with the dark green foliage. They are hardly ever attacked by insects or fungi.—Laburnum alpinum is the hardiest species and perfectly hardy as far north as Massachusetts; L. anagyroides is somewhat less hardy, while L. caramanicum is tender. They thrive in any kind of well- drained soil, including limestone, and grow as well in partly shaded positions as in sunny ones. Propagated by seeds, sown usually in spring, and also by layers; the varieties are mostly grafted or budded on seedlings of one of the species.
Laburnum anagyroides, Medikus (L. vulgare, Griseb. Cytisus Laburnum, Linn.). Golden- Chain. Bean-tree. Fig. 2053. Large shrub or small tree, to 20 ft., with erect or spreading branches: branchlets appressed - pubescent, grayish green: lvs. long-petioled; lfts. elliptic or ellipticovate, usually obtuse and mucronulate, glaucous - green and appressed - silky pubescent beneath when young, 1-1 3/4 in. long: racemes silky-pubescent, 4-8 in. long; fls. about 3/4 in. long: pod appressed - pubescent, with thick keel, about 2 in. long; seeds black. May, June. S. Eu. Gn. 25, p. 518; 34, p. 30, and 51, p. 302. G.C. III. 36:318. H. W. 3, p. 101.—There are many garden forms. Var. aureum, Rehd. (var. chrysophyllum, Schneid.), with yellow foliage. F.S. 21:2242, 2243. F. M. 1875: 182. G.Z. 20:129.
Var. bullatum, Schneid. (var. involutum, Hort.), with curled lfts. Var. Carlieri, Schneid. (L. vulgare Carlieri, Kirchn.). Lvs. smaller: fls. smaller in short upright racemes, often several from one bud. Var. pendulum, Rehd., with pendulous branches. Gn. 25, p. 522. G.M. 45:317. Var. quercifolium, Schneid., with sinuately lobed lfts. Gn. 25, p. 520; 34, p. 30. Var. sessilifolium, Schneid., with crowded, sessile lvs. Var. Alschingeri, Schneid. (L.Alschingeri, Koch). Racemes shorter, lower lip of calyx longer than upper lip: lvs. more silky. S. E. Eu. Var. autumnale, Rehd. (L. vulgare autumnale, Kirchn. L. vulgare bifera, Lavalle. L. vulgare, semperflorens, Nichols.). Blooms a second time in late summer.
Laburnum alpinum, Griseb. (Cytisus alpinus, Mill.). Scotch Laburnum. Shrub or tree, to 30 ft., similar to the former: branchlets glabrous or hirsute when young: lfts. usually elliptic, acute, light green and glabrous beneath or sparingly hirsute, ciliate, 1-1 3/4 in. long: racemes long and slender, glabrous or sparingly hirsute; fls. smaller: pod thin, with the upper suture winged, glabrous; seed brown. June. Mountains, S. Eu. B.M. 176 (as Cytisus Laburnum). Gn. 25, p. 519; 34, p. 30. R.H. 1912, p. 446. G.M. 45:316. G. 36:477. Var. pendulum, Koch. With pendulous branches. Gn. 25, p. 522. A var. aureum is advertised.—This species flowers about 2 weeks later than the former, and has much longer and more slender racemes; it also is of more upright and stiffer growth and hardier.
Laburnum watereri, Dipp. (L. Parksii, Hort. C. alpinus x C. vulgaris, Wittst.). Hybrid of garden origin, but found also wild. Lvs. beneath and racemes sparingly pubescent: racemes long and slender: pod with narrow wing, sparingly appressed-pubescent, few-seeded. G.24:355. G. M. 45:313.—As hardy as L. alpinum and sometimes considered to be a variety of that species.
Laburnum adamii, Kirchn. (C. Adamii, Poir. C. Laburnum purpurascens, Loud. Laburnocytisus Adamii, Schneid. L. vulgare x Cytisus purpureus). Originated at Vitry, near Paris, about 1826. Habit and foliage usually almost like L. anagyroides, but fls. dull purplish, rarely yellow; sometimes bearing a few branches with the fls. and lvs. of Cytisus purpureus. A very interesting form, but of less ornamental value. B.R. 1965. B.H. 21:16-18. G.C. III. 36:219; 50: 162.—One of the so- called graft-hybrids which have recently been termed chimaeras, as there is no fusion of cell-contents and nuclei, but only a mixture of tissues.
L. caramanicum, Benth. & Hook. (Podocytisus caramanicus. Boiss.). Erect shrub, to 4 ft., much resembling in foliage and habit the Cytisus sessilifolius, with long and slender terminal upright racemes. July-Sept. Asia Minor. R.H. 1861, p. 410. G.C. III. 48:454. B.M. 7898.—L. fragarans. Griseb., L. ramentaceum, Koch, and L. Weldeni, Lavalie.—Petteria ramentacea.
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