Introduction
This is an airy, graceful, deciduous tall shrub or small tree, growing to a maximum of 20 to 25 feet, with rich, yellow wisteria-like, drooping flower panicles, up to 10 inches long, which appear in late spring or early summer. The tree is truly incredible in full bloom. It is difficult to grow but if tried should be grown in a spot protected from full day sun, with very well-drained, alkaline pH soil and high organic matter. It tolerates alkaline soil but not wet soil, and does not grow well in soil below pH 7.0.
General Information
Scientific name: Laburnum spp.
Pronunciation: luh-BER-num species
Common name(s): Goldenchain Tree
Family: Leguminosae
USDA hardiness zones: 5B through 7B (Fig. 2)
Origin: not native to North America
Invasive potential: little invasive potential
Uses: specimen; deck or patio; espalier; container or planter
Availability: not native to North America
Description
Height: 20 to 25 feet
Spread: 12 to 18 feet
Crown uniformity: irregular
Crown shape: upright/erect
Crown density: open
Growth rate: moderate
Texture: medium
Foliage
Leaf arrangement: alternate (Fig. 3)
Leaf type: trifoliate, odd-pinnately compound
Leaf margin: entire
Leaf shape: elliptic (oval), obovate
Leaf venation: pinnate, reticulate
Leaf type and persistence: deciduous
Leaf blade length: less than 2 inches, 2 to 4 inches
Leaf color: green
Fall color: no color change
Fall characteristic: not showy
Flower
Flower color: yellow
Flower characteristics: very showy
Fruit
Fruit shape: elongated, pod or pod-like
Fruit length: 1 to 3 inches
Fruit covering: dry or hard
Fruit color: unknown
Fruit characteristics: does not attract wildlife; not showy; fruit/leaves a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; not showy; typically one trunk; thorns
Pruning requirement: needed for strong structure
Breakage: resistant
Current year twig color: green
Current year twig thickness: medium
Wood specific gravity: unknown
Culture
Light requirement: full sun
Soil tolerances: sand; loam; alkaline; well-drained
Drought tolerance: moderate
Aerosol salt tolerance: none
Other
Roots: not a problem
Winter interest: no
Outstanding tree: yes
Ozone sensitivity: unknown
Verticillium wilt susceptibility: unknown
Pest resistance: resistant to pests/diseases
Use and Management
Goldenchain Tree is a good specimen, patio or border accent tree, and can also be espaliered against a wall. In USDA hardiness zone 7, young plants are extremely attractive but do not usually last long since the plant does not tolerate heat well. All parts of the plant are poisonous. Use as a novelty where a brightly-colored accent is needed in the spring. Do not overwater.
Laburnum alpinum is a related tree which is just as beautiful in flower.
Pests
Tree can be attacked by aphids or mealy-bugs.
Diseases
Leaf spot, laburnum vein mosaic and especially twig blight can be problems. Leaf-scald can also be a problem where bark is exposed to afternoon sun in winter. Root rot is also a problem in soil kept too moist.