Katsura tree (Cercidiphyllum)

Synonyms: Cercidiphyllum

Katsura tree (Cercidiphyllum Siebold & Zucc.) – a genus of trees in the family Cercidiphyllaceae. It was first described in 1846 in Abh. Math.-Phys. Cl. Königl. Bayer. Akad. Wiss. 4(3): 238 by Ф.Ф. Забольдом and Й.Г.Цуккарини. The genus name derives from "cercis" – the Latinized Ancient Greek name for shrubs and trees of the legume family (meaning "high") and the Greek "phyllon" – leaf. In cultivation since 1865.

In the wild it occurs in Japan, China and on Kunashir Island. It grows in dense mixed and deciduous forests.

It is a dioecious deciduous tree, usually with several trunks at the base. Annual growth is continuous and the shoot-forming ability is good. The crown is broadly pyramidal. Bark fissured, dark gray. Shoots grayish-brown, young shoots brown and glabrous.

Leaves are heterophyllous: on auxiblasts opposite or nearly opposite, from broadly ovate to elliptic and almost triangular; on short shoots alternate, from broadly cordate to reniform. Leaf blade 4–10 cm long and 5–8 cm wide, dark bluish-green, glaucous or whitish beneath, with reddish veins; margins coarsely blunt-toothed; venation palmately looped. After unfolding the leaves are colored purplish-pink, in autumn they turn crimson or golden-yellow, with a sweetish scent. Petioles 1.5–4.5 cm long.

Flowers unisexual, wind-pollinated, without a perianth, pinkish, arranged in strongly reduced, compact racemes. Stamens 8–13, up to 9 mm long; filaments long, thin, pendulous; anthers long, 3–4 mm, reddish; connective short, conical. Gynoecium of 1 carpellate unit; style long, thin, pink-purple; stigma descending. Flowers before leaf emergence, in early May, lasting 6–7 days.

Fruit – a many-seeded pod-like one-carpel fruit, with winged seeds. Seeds brown, flat, trapezoid, 3–4 mm long. Fruit production begins at about 6 years; fruits ripen in late September.

Species: includes 2 species

• Cercidiphyllum japonicum Siebold & Zucc. – Japanese katsura (type species)
• Cercidiphyllum magnificum (Nakai) Nakai — magnificent katsura

Cultivars: 'Morioka Weeping', 'Amazing Grace', 'Tidal Wave', 'Aureum', 'Heronswood Globe', 'Ruby', 'Pendulum'.

Hardiness zone: zone 5a to 7b (-23°C).

Exposure: sun-loving, but can also grow in partial shade. Moisture-loving, relatively drought-tolerant.

Soil: not demanding in fertility, grow in ordinary garden soils, but most decorative on well-drained, fertile, slightly acidic loamy soil.

Soil mix: leaf mold, peat-compost and sand in a ratio of 2:1:1.

Planting: They do not tolerate burial of the root collar, which should be taken into account when planting, especially with large specimens.

Care: in hot, dry summers it is recommended to water the plant to maintain its ornamental appearance. Winter hardiness is fairly high, but it is recommended to mulch the root zone for winter with peat, peat-compost or wood chips, and also with a layer of fallen leaves.

Pruning: tolerates pruning well.

Propagation: readily propagated by green cuttings and by seed. About 60% of summer cuttings take root. Field germination does not exceed 10–20%. Spring sowing is preferred with seeds covered to a depth of 0.5–1.0 cm, lightly firmed and mulched with sawdust or peat mixed with sand. Regular feeding with mineral fertilizers in spring and summer is useful at the following rates: 10 g nitrogen, 15 g phosphorus and 20 g potassium per 1 sq. m of plantings, or apply the complex fertilizer "Kemira-Universal." Overall, plants grow fairly quickly, and with good cultivation their height by the end of the first summer can reach 40 cm. In mid-September first-year seedlings should be transplanted at a spacing of 15–20 cm.

Diseases and pests: practically unaffected.

Uses: ornamental for its distinctive crown and decorative leaves, brightly colored both at emergence and in autumn before leaf fall. Used for solitary and group plantings in gardens and parks.