NABF Newsletter #5

Feature #8

Pacific Yew as Bonsai

by David De Groot

Fig. 1. Pacific yew needles are dark green and slightly glossy on the upper surface, dull and pale green on the bottom. Actual length is about 5/8 inch. The female or seed cone (arid) is shown above the twig; the male or pollen cone is shown below it. Yews are dioecious, meaning the male and female cones are borne on separate trees.

Low to mid elevation forests on the west slope of the Cascade Mountains are generally dark, misty places. The crowns of old Douglas-fir, western hemlock and western red-cedar intermingle 70 feet or more above the forest floor, and heavily filter what meager light manages to penetrate clouds, fog, and persistent drizzle. Understory trees are few, but in widely scattered places, dark green mushroom shapes of foliage float like clouds above ground cover plants of sword ferns, huckleberries, and salal. Trunks and branches of these trees are often cloaked in moss or gone green with algae, but here and there strips of exfoliating bark have fallen away to reveal startlingly deep red, smooth under-bark. In old-growth forests where there is room to spread these trees are often less than 20 feet tall. In younger, denser commercial forests however, they often grow straight and narrow, sometimes as tall as 60 feet before either logging equipment or their narrow root systems cause them to topple. Branches from the fallen trees then continue to grow as shrubs, or even re-form into rows of interconnected trees. The extremely dark green color of the foliage makes Pacific yews conspicuous in the re-growth following logging, and they have elicited many false hopes in this writer as one by one, they prove to be growing from the trunk of a large prostrate tree, rather than on their own root systems.

Pacific yew (Taxus brevifolia) is said to have been an important tree to coastal Indians. Because the wood is fairly dense and quite hard, especially for a conifer, its primary uses were for weapons (bows, spears and clubs) and implements ranging from canoe paddles to combs. Modern commercial use of the wood is very limited, due to tree size and availability, although the beautiful color of the wood is prized by some wood carvers. The main commercial use today is the production of paclitaxel, a chemical used to produce the cancer fighting drug Taxol. Collecting the bark of wild trees has given way to the harvesting of small plants grown in nurseries.

Fig 2A. The author collected this yew in 1993 in the Green River area of western Washington. The trunk was carved in 1994, the first wiring was done in 1995, and it was transferred into this bonsai pot in 1995.

Collecting Pacific yew is a challenge because so many are growing from stumps or logs rather than on their own root systems. In some cases, layering the plant from its parent is possible. The ground-layering should be initiated in autumn to take advantage of seasonal rains, and might take up to two years to complete. Even collecting a yew on its own root system is challenging, as it gets very stressed from bare-rooting, and it is very difficult to withdraw it from loose, rocky mountain soil with the root/soil ball intact. The result is that a fairly high percentage of collected trees fail, but if they survive the initial transplanting, they prove to be long-lived, tough, and undemanding.

Fig 2B. The same tree as above in 2003.

Yews accept a wide variety of potting mixes, from all-organic matter to all mineral, but adapting from one soil type to another is stressful for them, and they will shed needles in response to stress. If the terminal buds remain undamaged, the tree will recover, although the recovery period is usually about two years. If the terminal buds die, the branch carrying them will also die. Healthy yews, however, can have all the terminal buds cut off (as in shearing) and quickly grow back. Yews (Taxaceae family), and bald cypresses and redwoods (Taxodiaceae family) are notable among conifers for their ability to re-grow from the stump, so even very hard pruning is not a problem, as long as the root system is in good shape. Once established in container cultivation, the root system becomes fibrous and dense, and tolerates repotting well.

The Pacific yew has branches that are soft when young, hard but not brittle when old, so it tolerates wiring quite well, although a few twigs are usually lost in the process. It is also slow growing, which means it can hold wire for a pretty long time – a couple of years, unless the wired branch is bent sharply or allowed to bolt. It is comfortable to work with, because the pointed needles are not sharp. Branches are wired into layered pads, the same as is done with Japanese yew. Trimming can be done by cutting back to a smaller side branches, and buds are pinched as for other short leaf conifers, but unlike firs, spruce, hemlocks, etc., cutting back twigs can be done at virtually any time of year, especially if pre-formed buds are visible at the base of the needles. Yew wood is not particularly resinous, but dead wood remains intact for a long time, so jin and shari are practical.

Fig 3A. A commercially collected Pacific yew purchased in 1999.

The species name “brevifolia” indicates that the needles of Pacific yew are shorter than those of other species, and they often have a slightly olive cast, compared to English yews. Pacific yews are understory trees in nature, so they are very shade tolerant, and even shade grown trees have attractively compact foliage. They tolerate full sun, but will sometimes take on a bronze color, especially if exposed to sun and heat together. Moving a yew from a shady to a sunny location can turn the foliage almost orange, and cause some defoliation. Usually, the new foliage that forms in the sun will be adapted to it, and have a normal green color. If bronzing continues to be a problem, move the affected tree to open shade or place under a 50% shade cloth.

Fig 3B. A workshop instructor produced this concept in 2002.

Pacific yews grow in maritime climates where there is abundant moisture, so they enjoy frequent watering, especially in hot weather, as long as their soil drains well. They do not like being in soggy soil for long periods of time. Likewise, allowing them to dry out will cause needle discoloration, some needle drop, and possibly the death of some twigs. Pacific yews need chilling hours (temperatures below 50 degrees F) to complete their annual cycle. They tolerate months of cool to cold weather, but again, as they are native to maritime zones from the southern tip of the Alaskan panhandle to near San Francisco, they cannot tolerate the extreme cold of the upper Midwest and Northeast winters without protection.

Fig 3C. Due to sparse branching on the lower trunk, the plan is altered to allow a taller design.

All in all, Pacific yew is one of the best of our native trees for bonsai cultivation, and it deserves a more prominent place in our collections.

Fig 3D. After the initial pruning and wiring