Japanese Tree Lilac Syringa reticulata

Japanese tree lilac is a small deciduous tree or large shrub in the olive family (Oleaceae). The tree is native to Japan and is found growing on cliffs. The species epithet, reticulata, means "netted veins" and refers to the plant's leaves.

Plant in full sun in organically rich well-drained acidic soils. It will tolerate heavy clay soils and urban conditions along with browsing by deer. This tree will tolerate partial shade; however, full sun is required for prolific flower production. Good air circulation is also recommended.

The Japanese tree lilac grows to a height of 30 feet tall and may be single or multi-stemmed with an oval to rounded canopy. The bark is reddish brown with distinctive, horizontal lenticels. The leaves are dark green, pubescent on their undersides and have a drooping habit. The flowers bloom in June and are borne in short, axillary panicles. The creamy-colored flowers are scented and last only 2 weeks. They lack the sweet fragrance typically associated with lilacs and have more of a privet-like odor (see Ligustrum lucidum). The blooms are followed by clusters of green and then yellow capsules that can persist through winter. Its showy fragrant blooms attract hummingbirds, insect pollinators, and butterflies. The tree also provides shelter and habitat for wildlife.

The Japanese tree lilac would be a nice addition to the patio area to provide flowers in the late spring to early summer and shade for the summer. It is the most trouble-free lilac. It may also be considered as a street tree, large hedge, or an accent or specimen for a shrub border.

Quick ID Hints:

• the bark has prominent horizontal lenticels
• exfoliating, reddish-brown bark when young, and the bark becomes scaly and gray with age 
• the leaves are dark green, simple, broad-ovate to ovate with sharp tips and a drooping habit
• the flowers are creamy-colored panicles measuring 6 to 12 inches long and bloom in June for 2 weeks
• the fruits are clusters of warty, dry, and green to yellow capsules that appear after the flowers and persist through the winter
• the buds have 4 pairs of scales and are brown and sessile

Insects, Diseases, and Other Plant Problems: The Japanese tree lilac has no serious insect or disease problems. It tends to be resistant to powdery mildew, bacterial blight, scale insects, and borers.

VIDEO created by Grant L. Thompson for “Trees, Shrubs, and Woody Vines for Landscaping” a plant identification course offered by the Department of Horticulture at Iowa State University.