Like last week’s Philesia magellanica, today’s species is also a member of a family containing only two species. In this instance, though, both species are within the same genus, Cercidiphyllum.
Douglas Justice, Associate Director of Horticulture and Collections at UBC BG, is responsible for the rest of today’s entry. These are excerpts from the Vancouver Trees app:
A native of temperate eastern China and Japan, Cercidiphyllum japonicum is a fast growing deciduous tree with a broad, rounded crown. The species is particularly valued for its strongly ascending, often multiple stems, attractive, rough bark and tiered, well spaced, sweeping branches. Katsuras are texturally unlike most other trees, growing 20 to 30 m tall with prominent bunches of radiating branches at the ends of main scaffold branches. As well, long-lived short shoots naturally develop along the branches. Each short shoot bears a single leaf in the growing season and extension growth is limited to a few millimetres annually. Much like in ginkgos and larches, the prominence of the short shoots over normal extension shoots increases with age, giving the un-shaded interior branches of mature katsuras a leafy, well-clothed look in summer and a somewhat knobby, but not unattractive appearance in winter.
Cercidiphyllum species are wind-pollinated and dioecious. Leaf emergence is preceded by the opening of hundreds of tiny, scarlet, apetalous flowers on the short shoots that line the mature branches. The finest of spring days start by seeing the flowers catching the morning sun, like so many tiny rubies. On female trees, the fertilized flowers turn into clusters of tiny, up-standing pea-pod-like follicles. Cercidiphyllum is classified in its own family (Cercidiphyllaceae); its closest relatives include species of the Altingiaceae (the sweetgums) and Hamamelidaceae (the witch hazels).
The new leaves of most katsuras emerge copper or bronzy green, although darker red or even purple new foliage is also known, and they are accompanied by thin, caducous stipules. Katsura leaves are ovate to rounded, with a cordate base, not unlike those of Cercis, hence Cercidiphyllum, from kerkis = redbud + phyllon = leaf. They are about 5 to 9 cm across with impressed veins and crenate, recurved margins. The leaves are borne oppositely, or sometimes sub-oppositely, along the long, slender shoots. Those produced from short shoots are usually larger and more rounded. The leaves are exceptionally waxy, often glaucous below and dull above, shedding rain in rivers of beads. The dull leaf waxiness seems to enhance the absorption and transmission of light through the canopy, rather than reflecting it away. In autumn, the leaves glow in modest fiery tones of yellow, coral pink, red and black purple, usually a branch at a time, although shaded plants typically turn pale translucent yellow. If that wasn’t enough to recommend the genus, the senescing leaves of katsuras smell of burnt sugar—strawberries, ripe apples or candy-floss to some—a deliciously pervasive fragrance around any specimen in autumn, as well as during prolonged summer droughts.
The tall, elegant weeping katsura, Cercidiphyllum japonicum ‘Morioka Weeping’, has strongly upright primary shoots and pendulous side branches (essentially, an excurrent habit). Plants can become tall and wide spreading (10 × 7 m after 25 years), with several upright stems and numerous gracefully cascading branches, not unlike a narrow weeping beech. ‘Morioka Weeping’ is an ancient Japanese clone known from before 1635, but modern stocks are all derived from an individual plant collected at the Ryugenzi Temple near the city of Morioka in northern Japan. It is often listed in the trade incorrectly under the name Cercidiphyllum magnificum ‘Pendulum’, but it is definitely a Cercidiphyllum japonicum cultivar. ‘Morioka Weeping’ is a staminate (hence, seedless) cultivar.