Cephalotaxus harringtonii / Japanese plum-yew

Cephalotaxus harringtonii, as described in 1974 by Siro Kitamura in Acta Phytotaxonomica et Geobotanica, 26th edition, is commonly known Japanese plum-yew or Cow's-tail pine; as well as イヌガヤ(Inugaya) in the Japanese language. It is the type-species of the Cephalotaxus genus.

This species has been in cultivation in Europe since 1829. Many modern horticulturists are familiar with this Japanese species, named in honor of Charles Stanhope, the 4th Earl of Harrington, one of the first to grow the plant in a European garden, at Elvaston, United Kingdom.

The Japanese plum-yew was first considered to be a yew when it was partially described by Thomas Andrew Knight in 1839 and as such was named Taxus harringtonii. It was then moved into the current genus by Philipp Franz von Siebold and Joseph Gerhard Zuccarini in 1846, but with a new specific name, making the new name Cephalotaxus drupacea. Some botanists consider C. koreana and C. sinensis to be synonymous with C. harringtonii.

This conifer is usually found under the name Cephalotaxus harringtonia, a name that violates the grammar rules of Botanical Latin and in 2012 was corrected to Cephalotaxus harringtonii. However, this opinion is still not universally accepted by taxonomists and therefore it is acceptable to use Cephalotaxus harringtonia until a definitive position has been agreed.

Description. Japanese Plum-yew is a an evergreen coniferous bush or small tree in the Cephalotaxaceae family. It grows to mature heights of 35 feet (10 m) tall with spreading branches and a broadly rounded crown.

• Bark is gray, peeling longitudinally in thin strips.
• New shoots remain green for 3 years after forming and have ribs at the leaf bases.
• Foliar buds are green in color, with a globose shape and very small in size, measuring only 0.04 inch (1 mm) long.
• One rank of leaves is present on either side of the shoot, rising above it and curving slightly inwards, forming a narrow V-shape somewhat akin to a dove's wings. The ranks are often vertical, but can be more flattened in shaded parts. Individual leaves are broadly linear in shape and measure about 2 inches (5 cm) long by 0.12 inch (3 mm) wide. They are abruptly pointed at the apex, leathery in texture and a bright matte yellowish-green on the upper-surface. The abaxial surface, or underside of the leaves, shows two broad, pale to silvery stomatal bands.
• This species is dioecious and the male plants are typically densely covered with pairs of pollen cones that are pale cream in color, becoming brown with time, and globular in shape. They are borne on 0.08 to 0.16 inch (2 - 4 mm) stalks beneath each pair of leaves. Pollen is released from March until May.
• Female plants have two pairs of knob-like globose flowers that appear on curved stalks at the bases of the shoots. Arils (seed cones) are obovoid in shape and measure 1 inch (2.5 cm) long by 0.6 inch (1.5 cm) wide. They have a smooth texture and pale green color with dark green stripes that turn brown when ripe.

Distribution. This species is native to Japan— from Kyūshū in the south to Hokkaidō in the north. More specifically, it is found in Hondo in the Chiba Prefecture on Mount Kiyosumi, which is located in the Awa District within the Awa Province. It is also found in the Nagasaki Prefecture and the Hiroshima Prefecture where it thrives in partial shade on deep, rich soils.

Hardy to USDA Zone 7, cold hardiness limit between 0º to 10ºF (-17.7° and -12.2°C).

C. harringtonii has been in cultivation in the United Kingdom since 1829 and is infrequently encountered as a garden specimen. Of the several species that exist in the genus, the Japanese plum-yew is the one most often encountered in western gardens.

An Australian company, ChemGenex Pharmaceuticals Ltd., is developing a leukemia therapy called Omacetaxine derived from the leaves of this species.

Attribution from: Kim E. Tripp; Cephalotaxus: the plum yews; ©1995, Arnoldia 55(1): 24-39.