Sophora japonica
Japanese pagoda tree
China and Korea (dry mountain forests and valleys); widely cultivated in Japan since antiquity
Overview
Sophora japonica (reclassified by current authorities as Styphnolobium japonicum) is a deciduous tree in the legume family (Fabaceae spp.) reaching 40–60 feet (12–18 m) tall with a spread of 40–60 feet (12–18 m). The habit is broad, rounded, and spreading with a dense crown. The species is native to China and Korea; the epithet 'japonica' reflects its long introduction to Japan rather than its origin, and earlier Western botanists encountered the tree in Japanese temple grounds. Pinnately compound leaves 6–10 inches (15–25 cm) long carry 7–17 small ovate leaflets 1–2 inches (2.5–5 cm) each, giving the canopy a lacy open texture at close range. Large terminal panicles 8–15 inches (20–38 cm) long of small pea-shaped creamy-white to pale-yellow flowers open in August–September, later than most large shade trees, and are followed by pendulous yellow-green seed pods 3–8 inches (8–20 cm) long that persist into winter. Young branches retain green bark. Growth rate is moderate at 13–24 inches (33–60 cm) per year. Hardy to zone 5. Trees typically take 10–15 years to begin flowering, and the annual flower and pod drop creates litter on patios, walkways, and parked vehicles. Seeds contain cytisine alkaloids and are toxic to humans and animals if ingested.
Native Range
Sophora japonica (Styphnolobium japonicum) is native to China and Korea, where it grows in dry mountain forests and valleys. The species is widely naturalized in Japan through centuries of temple and garden cultivation, which is the source of the Linnaean epithet.Suggested Uses
Grown as a shade tree in parks, large residential gardens, and wide boulevard plantings at 40–60 foot (12–18 m) spacing. The August–September bloom fills a late-summer gap when few large trees are in flower. Urban tolerance suits civic plantings away from pedestrian surfaces where flower and pod drop would cause slip hazards or staining. Small gardens, container culture, and sites directly over patios, walkways, or parking produce poor results or ongoing cleanup. Seeds are toxic, so the tree is not sited where children or livestock graze fallen pods.How to Identify
Appearance
Size & Dimensions
Height40' - 60'
Width/Spread40' - 60'
Reaches mature size in approximately 30 years
Bloom Information
Large terminal panicles 8–15 inches (20–38 cm) long of small pea-shaped creamy-white to pale-yellow flowers open in August–September. Flowering in late summer places this species after most large shade trees have finished blooming. Trees typically take 10–15 years after planting before the first flowering, and mature trees produce heavy flower crops in alternate years. Pendulous yellow-green seed pods 3–8 inches (8–20 cm) long follow the flowers and persist into winter.
Detailed Descriptions
Flower Description
Creamy-white to pale-yellow, small pea-shaped in terminal panicles 8-15 inchesFoliage Description
Dark green; pinnately compound 6-10 inches with 7-17 ovate leaflets; lacy open canopyGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grows in full sun in well-drained soil at pH 6.0–8.0, tolerating clay, loam, and sand. Hardy to zone 5. Drought, heat, air pollution, alkaline soils, and urban conditions are all tolerated once established. Flower and pod drop creates persistent litter; siting over patios, parked cars, and high-traffic walkways leads to staining and slip hazards. Seeds contain cytisine alkaloids and ingestion causes toxicity in humans and animals.Pruning
Prune in late winter (February–March) before bud break. Establish a central leader in the first 5–10 years, remove crossing or competing co-dominant stems, and thin the crown lightly to reduce wind resistance. Mature trees need only selective deadwood removal every 3–5 years.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
early spring