Seven Sons Tree (Heptacodium miconioides) — identification, habitat & look-alikes

Seven-son flower is a large shrub from China that blooms in late summer, when few other trees and shrubs do, with clusters of fragrant white flowers that draw bees and butterflies. After the petals drop, the swell and turn red, keeping the plant colorful into fall. Rare in the wild, it has become a popular garden plant in the US since seed arrived in 1980.

Appearance

Appearance: Pale tan bark peels in long papery strips, adding winter interest.
Growth form: A deciduous large shrub or small tree, 13–30 ft (4–9 m) tall, usually multi-stemmed with arching branches. It grows fast, reaching about 10 ft (3 m) in five years, and can be pruned to a single trunk to show off the bark.
Leaves: Opposite, smooth-edged, oval leaves 3–6 in (8–15 cm) long, with three strong veins running from the base toward the tip. They tend to droop and curl inward, and often drop in fall without much color.
Flowers: Small, fragrant white flowers in clusters at the branch tips. After flowering, the sepals grow from about 1/10 in to 1/3 in (2–10 mm) and turn red, most vividly in warm, dry autumns.
Flowering time: Peaks in August and September in cultivation, and can continue until the first frost. Around Boston it flowers from mid-August into early October.
Fruit: A dry, silky-haired seed about 3/8 in (1 cm) long, topped by the enlarged red .

Where it lives

Typical habitats: Gardens and parks
Arboretums
Range: Native only to a few mountain areas of eastern China, where the known wild populations are in Anhui and Zhejiang provinces; it was first found in Hubei. It grows in scrub and forest edges, often on cliffs, at about 2,000–3,300 ft (600–1,000 m). In the US it is grown in gardens and is not considered invasive anywhere in the country.
Preferred conditions: Very cold-hardy, rated to USDA zone 5 and surviving about −31 °F (−35 °C). Grows in most soils but shouldn't dry out too much in summer, and it tolerates shade well.

Growing it

Propagation: Seed sprouts readily without a cold period. Softwood or semi-ripe cuttings taken in late spring or early summer root easily.

Conservation

IUCN Red List: VUVulnerableHigh risk of extinction in the wild
Status: Habitat loss is the main threat, and it has second-class national protection in China.

Culture and stories

Culture and stories: The common name translates the Chinese name 七子花. Each little cluster has six flowers around a central bud, a 3 + 3 + 1 arrangement that gives the "seven."
Plant hunter Ernest Wilson found it in western Hubei in 1907 but didn't collect seed. Seed reached the Arnold Arboretum in Boston and the U.S. National Arboretum through the 1980 Sino-American Botanical Expedition, and most plants in cultivation descend from that Arnold Arboretum stock.