Sophora species grows to a height of 40 to 60 feet and spread of 30 to 45 feet, forming a fine-textured, round canopy even as a young tree (Fig. 1). It has a rapid growth rate and tolerates polluted city conditions, heat, and drought.
The tree prefers a sunny, open location on any light soil. 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 a dark grey with age. The species tree must be at least 10-years-old to bloom, but the cultivar ‘Regent’ blooms at six to eight-years-old.
Scientific name: Sophora japonica
Pronunciation: sah-FOR-uh juh-PAWN-ih-kuh Common name(s): Scholar Tree, Japanese Pagoda Tree Family: Leguminosae USDA hardiness zones: 5 through 8A (Fig. 2)
Origin: not native to North America Uses: large parking lot islands (> 200 square feet in size); wide tree lawns (>6 feet wide); medium-sized parking lot islands (100-200 square feet in size);
medium-sized tree lawns (4-6 feet wide);
recommended for buffer strips around parking lots or for median strip plantings in the highway; near a deck or patio; shade tree; specimen; sidewalk cutout (tree pit); residential street tree; tree has been successfully grown in urban areas where air pollution, poor drainage, compacted soil, and/or drought are common
USE AND MANAGEMENT
The tree drops flower petals creating a creamy white carpet for several weeks on the ground, but they can temporarily stain sidewalks. The yellow fruit pods form in late summer and are quite showy, dropping later in the winter and could be a nuisance to some people. But they are small and fairly easily washed away.
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. 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. This urban-tough tree is highly recommended for urban street tree planting. Also makes a nice mediumsized patio tree and is well-suited for parking lot planting, creating shade from its spreading canopy. It is adapted to restricted soil spaces, and tolerates
drought in reasonable soil and is tolerant of salt spray. Best when planted in full sun and well-drained, not wet, soil. Sophora species has a few cultivars: ‘Fastigiata’ – upright habit; ‘Pendula’ – weeping habit; ‘Princeton Upright’ – upright form suitable for narrow sites, somewhat smaller than the species; ‘Regent’ – oval crown and blooms at an early age, has glossy leaves which shed soot and dirt, readily available in nurseries.
Potato leafhopper kills young stems causing profuse branching or witches broom on small branches. It usually is not a problem on larger trees.
Sophora species is generally pest- and diseasefree. Occasionally, Scholar Tree will get a fungus canker about two-inches or less across, have 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.
Twig blight or dieback can be a problem occasionally. Prune out infected branches and avoid unnecessary wounding. Keep trees vigorous by regular fertilization. Powdery mildew forms a fungus mat which looks like a white coating on the leaves. The disease is usually not serious.