Cephalotaxus: the Plum Yews
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Cephalotaxus: The Plum Yews Kim E. Tripp The largest ~Japanese plum yews] I saw grow in the rich forests at the foot of Higashi-Kirishima ... I saw many trees from 8 to 10 m tall with ... wide-spreading branches forming broad rounded crowns. Such trees, with their dark-green leaves pale or glaucescent on the under side, are very beautiful.... E. H. Wilson, The Conifers and Taxads of Japan, 1916’ Wilson was describing the surprisingly large antecedents. Now the genus is restricted to specimens of Cephalotaxus harringtonia he had southern and eastern Asia-Japan, Korea, south, seen growing in Kyushu, Japan. Although it was central, and eastern China, Hainan, Taiwan, Wilson who introduced the plant into cultiva- India, Burma, Laos, and parts of Vietnam.4 tion in the United States, he was not the first Cephalotaxus was also found in Europe and Western plant explorer to collect it and extoll its northwestern North America in the Miocene beauties. Long before, around 1829, the promi- and Pliocene eras; moreover, during the Jurassic nent plant collector and principal author of era its antecedents extended into what is now Flora Japonica, Philipp Franz von Siebold, had Greenland.s sent Cephalotaxus to Europe where it was re- Because Japanese plum yew has been in culti- ceived with interest and appreciation.2 Siebold vation in Europe and the United States for grew five different Cephalotaxus in his own close to a century, many modern horticultur- garden in Japan, along with many other plants ists are familiar with the Japanese species he had discovered, cultivating them for their Cephalotaxus harringtonia, named in honor of beauty and for evaluation as garden plants. the Earl of Harrington, one of the first to grow Today, although plum yews are widely con- the plant in a European garden. Far fewer are sidered some of the most beautiful and useful of aware of other equally beautiful members of the evergreen conifers, their potential as ornamen- genus that were not found by Western explorers tal and medicinal plants has yet to be fully until the turn of the century. Six to twelve explored and utilized. The endangered status species and botanical varieties, depending on of Cephalotaxus in the wild-particularly in the taxonomist consulted, comprise an elegant China, its "distribution center and refuge,"3 genus with an inelegant name. where it is vulnerable to the increasing demands While today Cephalotaxus is most often con- of an exploding human population-lends a sidered the single genus of the coniferous sense of urgency to efforts to learn more Cephalotaxaceae, it was earlier included in the about this fascinating genus. At the Arnold Taxaceae with taxads like Torreya, Taxus, and Arboretum, we are working to help conserve Pseudotaxus.~ Distinctive aspects of the em- Cephalotaxus while continuing to study and bryogeny and development of Cephalotaxus set propagate the genus for use in cultivation. it apart from this group, however, in spite of shared adult morphological characteristics like Cephalotaxus fleshy seed coats, two-ranked needles of similar The modern natural range of Cephalotaxus has shape, and low shrub to small tree habits.’ A few diminished considerably from that of its early modern authors include Amentotaxus in the Cephalotaxus sinensis, seen here "d la mode" m last winter’s ice storm, is one of the most cold hardy of the Chmese plum-yew species. 26 The mature frmts of Cephalotaxus (C. sinensis is shown here) resemble olmes or small plums. Cephalotaxaceae, resulting in occasional refer- While the foliage of plum yews generally re- ences in the literature to two genera in the sembles that of true yews, the reproductive stro- Cephalotaxaceae.8 bili are quite distinct. Most of us are familiar Plum yew’s botanical name is apt. "Cephalo- with the bright red (or occasionally yellow), taxus" means "head-yew," from the Greek fleshy, nonpoisonous "aril" that incompletely "kephale" for head and the botanical name surrounds the yew’s very poisonous, small, "taxus" for the yew genus. "Head-yew" refers to rounded seed. Fewer are likely to be familiar the flowering structures that are borne in tight with the seed of plum yew, which is signifi- clusters or "heads" and to its needles, which re- cantly larger than that of yew, being about the semble those of yew. Another, more appealing size and shape of an olive or very small plum common name, plum yew, refers to the plum- (0.75 to 1.25 inches long and 0.25 to 0.75 inches like shape and color of the ripened fleshy wide) and completely enclosed by a thin, hard "cone." shell and an outer fleshy coat. As the seed Cephalotaxus is most often found growing as ripens, the fleshy coat changes color, maturing shrubs or small trees in soils rich in humus in from an attractive, glaucous blue-green, through moist subtropical or warm-temperate forests, a warm cinnamon-red (hence "plum yew"), and generally as understory plants in at least light finally to a dull tan or purple-brown before ab- shade. They are primarily low- to mid-altitude scission of the entire "cone" and/or degradation plants, but a few variant types are found at of the fleshy tissue. higher elevations and on chalky gravel cliffs. Male and female plum yew strobili are borne The entire range of the genus, however, extends on separate plants. Male strobili develop in flat- from tropical to cool temperate climates, and tened heads of numerous small clusters of cold hardiness of cultivated taxa corresponds to anthers, about 0.25 inches in diameter, regularly provenance. arranged in the axils of the needles along the 27 length of the branchlets. Female strobili develop useful materials, but as exquisitely beautiful as clusters of six to twelve ovules in pairs held evergreens for a variety of modern landscapes, on an odd-looking, oval, initially mauve-colored combining graceful habits and foliage with the head (or "cone"), that expands from about 0.5 tough stress resistance and ease of maintenance inches in length at first visibility to the mature required by modern gardeners and landscape length of 0.5-1.25 inches (depending on the spe- contractors. cies). Usually only one seed matures per head.9 Cephalotaxus are slow-growing conifers with Three to five female heads are borne on stalks at dark olive to black-green foliage. Because their or near the end of the current or previous year’s habits range from upright and shrubby to low branchlets.’° Female cones are wind pollinated. and informally mounding, they can serve as Seeds of Cephalotaxus have a relatively long hedges, masses, groundcovers, specimens, and period of development. Depending on species foundation or container plants. They thrive in and region, pollen cones require nine to eleven a variety of soils, including extremely dense months to mature (from initiation to pollen clays. They are not only tolerant of shade but- dispersal), while female cones can take as long with only one exception-perform well even as twenty-one months, generally maturing in heavy shade, an unusual trait for a needled at the end of the second growing season after evergreen. Indeed, most Cephalotaxus produce initiation." the best foliage when given at least some shade, Cephalotaxus is now rare and endangered in although some maintain excellent foliage color significant areas of its range.’2 Its lengthy seed in either full sun or shade. maturation period, combined with a dioecious Plum yews are extraordinarily heat tolerant reproductive habit and an often sparse natural in humid climates, another unusual trait for a distribution throughout much of its range, may needled evergreen. For this reason, they have contribute to the seemingly low frequency of been called "the yew of the south," although regeneration for the genus in the wild. Accord- they can serve as excellent landscape plants in ing to Huang, animals and birds may also eat the an area extending far beyond the Southeast. seed.’3 There is also pressure on Cephalotaxus Once established, they are tolerant of extended from human activity. It is harvested for timber dry periods such as those experienced during in various parts of its range as well as used most of our eastern summers. However, they for firewood and for medicinal purposes. The are not good choices for hot, dry climates like female cones are sometimes collected for the those in much of the southwestern United oil expressed from the seed. 14 States. Ironically, increasing awareness of the endan- Cephalotaxus are relatively deer resistant (I gered status of Cephalotaxus comes at a time have come to believe that no evergreen is totally when its potential value has expanded beyond deerproof). Deer feeding on plum yews have horticultural uses to include anticancer com- been reported in areas with very heavy deer pounds found in its seed and vegetative tissues. populations (for example, central New Jersey Experimental work with the ester alkaloids and Pennsylvania). Even in these cases, how- cephalotaxme, harringtonine, and allied chemi- ever, with only one exception, deer turned to cals has shown promise, although apparently no Cephalotaxus foliage only as a last resort. widespread therapeutic applications have yet Nomenclature and been introduced.’S Sadly, two of the three spe- Taxonomy cies that are especially rich sources of these Unfortunately, there is no current monograph alkaloids, C. hainanensis and C. oliveri, are on Cephalotaxus available. This is especially currently endangered, although the third, C. troublesome since the nomenclature of this fortunei, is less vulnerable.’6 genus is particularly confusmg and is likely to remain a challenge for the foreseeable future; to as a Garden Plant Cephalotaxus the best of my knowledge, no taxonomic mono- The various taxa of Cephalotaxus are of interest graph of the entire genus is currently underway.