Edward F. Gilman and Dennis G. Watson 2
Introduction
'Regent' scholar tree grows 40 to 50 feet in height with a spread of 30 to 40 feet, forming a large, rounded canopy even as a young tree. The canopy appears more uniform and predictable than the species. The dark green, shiny leaves turn yellow before dropping in fall. The very showy, greenish-white to yellow flowers are produced in mid to late summer and provide an airy feel to the tree for several weeks. A yellow dye can be made by boiling the dried flowers and buds in water. The young green twigs turn dark grey with age. The species tree must be at least 10-years-old to bloom but the cultivar 'Regent' blooms at two to eight-years of age.
General Information
Scientific name: Sophora japonica
Pronunciation: sah-FOR-uh juh-PAWN-ih-kuh
Common name(s): 'Regent' scholar tree, 'Regent' Japanese pagoda tree
Family: Leguminosae
USDA hardiness zones: 5B through 8A (Fig. 2)
Origin: not native to North America
Outstanding tree: yes
Invasive potential: little invasive potential
Uses: specimen; deck or patio; street without sidewalk; shade; parking lot island < 100 sq ft; parking lot island 100-200 sq ft; parking lot island > 200 sq ft; sidewalk cutout (tree pit); tree lawn 3-4 feet wide; tree lawn 4-6 feet wide; tree lawn > 6 ft wide; urban tolerant; highway median
Availability: not native to North America
Description
Height: 40 to 50 feet
Spread: 30 to 40 feet
Crown uniformity: symmetrical
Crown shape: round
Crown density: moderate
Growth rate: fast
Texture: fine
Foliage
Leaf arrangement: alternate (Fig. 3)
Leaf type: odd-pinnately compound
Leaf margin: entire
Leaf shape: ovate
Leaf venation: pinnate
Leaf type and persistence: deciduous
Leaf blade length: less than 2 inches
Leaf color: green
Fall color: yellow
Fall characteristic: not showy
Flower
Flower color: white/cream/gray, yellow
Flower characteristics: showy
Fruit
Fruit shape: pod or pod-like, elongated
Fruit length: 3 to 6 inches, 6 to 12 inches
Fruit covering: dry or hard
Fruit color: yellow, brown
Fruit characteristics: does not attract wildlife; 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: susceptible to breakage
Current year twig color: green
Current year twig thickness: thin, medium
Wood specific gravity: unknown
Culture
Light requirement: full sun
Soil tolerances: sand; loam; clay; acidic; alkaline; well-drained; occasionally wet
Drought tolerance: high
Aerosol salt tolerance: moderate
Other
Roots: not a problem
Winter interest: no
Ozone sensitivity: unknown
Verticillium wilt susceptibility: unknown
Pest resistance: resistant to pests/diseases
Use and Management
The tree drops flower petals creating a creamy white carpet for several weeks on the ground, but they temporarily stain sidewalks. The fruit pods drop later in the winter and could be a nuisance to some people. The leaflets are small, creating light shade beneath the tree and are mostly washed away with rain or fall into shrub beds or between the grass blades.
This urban-tough tree is highly recommended for urban street tree planting. The tree reportedly has a straight trunk, but the trees commonly need pruning and training to form one central trunk. Some trees come from the nursery with multiple trunks or branches clustered together at one spot on the trunk. Buy those with one central trunk growing up the center of the tree or prune the tree to a central leader to create a strong, durable structure. Space branches along the central leader to ensure good branch attachment. It may take several prunings to train the tree to the proper form.
'Regent' scholar tree has a growth rate which is faster than the species and tolerates polluted city conditions, salt, alkaline soil, heat, and moderate drought. The tree prefers a sunny, open location on any light soil but trees perform poorly on clay or poorly-drained soil.
'Princeton Upright' has a narrower crown.
Propagation is by cuttings, grafts, or seed, though seedling trees of 'Regent' can take as long as the species to flower, 10- to 12-years.
Pests
This tree is pest-resistant. 'Regent' scholar tree is reportedly more resistant than the species to the potato leafhopper which kills young stems causing profuse branching, or witches broom, on small branches.
Diseases
Sophora species is generally not affected severely by diseases. A canker fungus forms cankers two-inches or less across with raised reddish-brown margins and light brown centers. The infected stem is killed when the fungus girdles the stem. Another fungus is sometimes found on dead branches on Sophora species. Frost injury may give both fungi an entrance into the tree. Prune out dead, damaged, or diseased branches.
If infected by twig blight or dieback, then prune out infected branches and avoid unnecessary wounding. Keep trees vigorous by regular fertilization.
Powdery mildew can infect the surface of the leaves.
