158 THE GREAT LAKES BOTANIST Vol. 57 HOW LARGE CAN TAXUS CANADENSIS GROW? Susan Fawcett Pringle Herbarium, Department of Plant Biology University of Vermont, 111 Jeffords Hall, 63 Carrigan Dr. Burlington VT 05105 [email protected] Anton A. Reznicek University of Michigan Herbarium 3600 Varsity Drive Ann Arbor, MI 48108 Sherwin Carlquist (1974) proposed that the evolution of insular woodiness is favored in part by a moderated climate. Proximity to the ocean buffers the ex - tremes of temperature and humidity and, together with the absence of large her - bivores, fosters the evolution of increased stature in many angiosperm families, frequently in conspicuous contrast to their continental herbaceous relatives (see Baldwin et al. 1998). Perhaps these same conditions, which are characteristic of the climate of South Manitou Island in Lake Michigan, but operating on a much shorter timescale and acting on phenotypes, have promoted the growth of three state champion trees and shrubs, including a national champion (Ehrle 2006), on an island only three miles wide by three miles long. As Voss and Reznicek noted (2012), Taxus canadensis Marshall (Canada yew) is “favored by the moist winds from Lake Michigan and [is] often luxuri - ant on forested dunes and in coniferous forests near the shore,” as is true in the present case. On August 16th, 2017, we encountered an individual of Taxus canadensis of unusually great size that we here register as the state champion, confirmed by Ted Reuschel, the current Michigan Big Tree Coordinator. Using the method described in Ehrle (2006) (which uses the US customary system fa - vored by foresters), we documented its size, and submitted our nomination to the Michigan Big Tree Database (Michigan Botanical Club 2018), the official reg - istry maintained by the Michigan Botanical Club for the past 65 years. The indi - vidual exhibits a dominant central trunk (Figure 1) and spreading crown (Figure 2). We measured a height of 15 feet (4.6 m), diameter at breast height of 2.3 inches (5.9 cm), and average crown spread of 5 feet 4 inches (1.6 m). This gives a total point score of 23.5, that is girth in inches at 4½ feet plus height in feet plus ¼ of the average crown spread in feet. The plant is located north of the trail towards the Valley of the Giants (the name given to a stand of immense old- growth Thuja occidentalis L.) a few hundred yards northwest of the Lighthouse on South Manitou Island, Leelanau County, 45.008°, –86.096°. The individual was discovered in sandy soil, in a vegetation zone transitioning from dunes to mixed conifer–hardwood forest. The adjacent forest supported extensive devel - opment of Taxus canadensis in the understory, where many clones formed thick - 2018 THE GREAT LAKES BOTANIST 159 FIGURE 1. Habit of champion Taxus canadensis , height of 4.6 meters, South Manitou Island, 2017. Photo by Anton A. Reznicek. ets of ascending branches reaching 2 m. This single slightly leaning stem was in the center of an old clone where the canopy was more open, perhaps from past tree falls. Taxus canadensis is the sole member of the conifer family Taxaceae that is 160 THE GREAT LAKES BOTANIST Vol. 57 FIGURE 2. Bark on central trunk of champion Taxus canadensis , South Manitou Is - land, 2017. Photo by Anton A. Reznicek. native to Michigan. It may be easily distinguished from the other conifers in the state by its lack of a resinous odor, its needle-like leaves that are strongly decur - rent and persistent, and seeds that are surrounded by a scarlet berry-like aril quite unlike the cones in the Pinaceae and Cupressaceae (Voss and Reznicek 2012; Barnes et al. 2016). It is the smallest species of Taxus worldwide and the only one that is consistently a modest shrub, with heights of 0.5-2 m given in all standard references (Eckenwalder 2009; Debreczy et al. 2011; Farjon 2017). It also has the smallest leaves and seeds of any species of Taxus —the leaves are typically under 2 cm long and less than 2.5 mm wide. It is the only monoecious species of Taxus , thereby readily distinguishing it from all of its congeners (Wil - son et al 1996; Eckenwalder 2009). The other eight to ten species of Taxus are all small to large trees, although exceptional dwarf or decumbent forms are known in T. baccata L. and T. cuspidata Siebold & Zucc. The maximum heights for species other than T. canadensis is given as 6–30 (–45) m (Eckenwalder 2009; Debreczy et al. 2011; Farjon 2017). Only the East Asian Taxus cuspidata is known as a sporadic escape in populated areas of southernmost Michigan (Voss and Reznicek 2012). Taxus canadensis is one of the forest understory species that is most affected by deer herbivory, and, although there are accounts of dense stands of large indi - viduals of T. canadensis at least as tall as a person, this situation is unknown 2018 THE GREAT LAKES BOTANIST 161 today except in the few rare areas sheltered from deer. There is therefore no reli - able information on the ultimate height that T. canadensis can achieve. In North America, the rare endemic, Taxus floridana Nutt. Ex Chapm., the Florida yew, and Taxus brevifolia Nutt., the Pacific yew have had representatives in the Na - tional Register of Champion Trees (American Forests 2018) since 1986 and 1959, respectively, but there is no record for Taxus canadensis . This is unsur - prising, since it is generally considered a “low, straggling, multistemmed shrub . to 2m” (Barnes et al. 2016). The other state champion trees from South Manitou include two additional conifers and a maple: Juniperis communis var . depressa Pursh (2006), Acer spi - catum Lam. (1969, superseded a decade later by the national champion, discov - ered in Houghton County, Michigan), and, most notably, the historic national champion northern white cedar, Thuja occidentalis, a 113-foot tall tree that has recently died and is now replaced by the new state champion in the same grove, which is 81 feet in height and was reported in 2006. An additional 12 state cham - pions are reported from Leelanau county across the strait separating South Man - itou from the Michigan Mainland, most of them in the vicinity of Sleeping Bear Dunes National Lakeshore (and subject to the moderating influence of Lake Michigan). Among these are four current or former national champions, Salix petiolaris Sm. (1975), Salix purpurea L. (1971), Cornus rugosa Lam. (1965) and Betula papyrifera var . cordifolia (Regel) Fernald (1972) (Ehrle 2003, 2006). The great size obtained by Thuja occidentalis in the Valley of the Giants was possible only because these trees withstood the extensive deforestation and sub - sequent fires of the logging era. Their survival has been popularly attributed to the sand incorporated into their bark, owing to their location on the back of the active dune, thereby dulling the sawblades of any lumberman who sought to fell them. Both islands were heavily logged in the late 1800s through early 1900s. South Manitou was an especially popular target during the heyday of Great Lakes shipping because of its natural deep water harbor and abundant timber, serving as a convenient stopover for refueling steamships en route between Chicago and the Straits of Mackinac (Hatt et al. 1948). None of the other cham - pions of South Manitou is considered valuable as a timber species. In addition to the equable climate, the absence of deer has allowed Taxus canadensis to thrive on South Manitou Island, in stark contrast to North Manitou Island, where the species was extirpated by the introduction of white-tailed deer in 1926 (Case and McCullogh 1987). As early as 1947, Leopold et al. (1947) rec - ognized the devastating impact of deer over-abundance on plant communities in the Great Lakes region, and especially on the highly palatable, low-growing Taxus canadensis , which, as early as 70 years ago was largely extirpated from vast areas of New York, Pennsylvania, Wisconsin and Michigan. Sadly, this long- lived, slow growing species has become quite rare throughout Michigan as a re - sult of deer browse (Barnes et al. 2016), an effect strikingly confirmed by exclo - sure studies (e.g., Allison 1990; Holmes et al. 2009), or that can be witnessed by visiting the deer and rabbit exclosure that has been maintained on Bois Blanc is - land in Lake Huron since 1956 by the Michigan Department of Natural Re - sources. With mounting evidence demonstrating the continued disastrous, and in some 162 THE GREAT LAKES BOTANIST Vol. 57 cases irreversible, impacts by the over-abundance of deer on plant communities, especially harmful to formerly dominant species of conifers including Tsuga canadensis (L.) Carrière , Thuja occidentalis , and Taxus canadensis (Stromayer and Warren 1997), isn’t it time to reconsider our management goals? We agree with the conclusion of Leopold et al. (1947) that “in managing overlarge herds, ‘too little and too late’ is the worst possible policy.” ACKNOWLEDGMENTS We would like to thank two anonymous reviewers for helpful comments on the manuscript. LITERATURE CITED Allison, T. D. (1990). The influence of deer browsing on the reproductive biology of Canada yew (Taxus canadensis Marsh.). Oecologia 83: 523 –529. American Forests. (2018). Champion trees national register. Available at https://www.american - forests.org/get-involved/americas-biggest-trees/champion-trees-national-register/ (Accessed Sept. 5, 2018). Baldwin, B. G., D. J. Crawford, J. Francisco-Ortega, S. C. Kim, T. Sang, and T. F. Stuessy. (1998). Molecular phylogenetic insights on the origin and evolution of oceanic island plants. Pp. 410 –441 in Molecular systematics of plants II. DNA sequencing, D. E. Soltis, P. S Soltis, and J. J. Doyle, ed - itors.