Botanist Interior 43.1

2006 THE MICHIGAN BOTANIST 59

DAPHNE MEZEREUM L. (THYMELAEACEAE) IN WISCONSIN

Thomas L. Eddy 426 Walker Avenue Green Lake, Wisconsin 54941 [email protected]

The introduction of “invasive alien species” (IAS) has and continues to cause substantial changes and disruptions to ecosystems worldwide (Elton 2000; Wilcove et al. 1998; Wilson 1992). The globalization of species, that is, the spread of other species throughout the world by human activities, is exacerbated by the flourishing trade of a globalized economy (Meyer 2005). Davis (2003) summarizes the conclusions of others when he states: “The globalization of Earth’s biota is transforming local and regional floras and faunas.” Clout and Poorter (2005) concur that IAS are a major threat to biological diversity on a global scale, and to prevent plant invasions requires international cooperation. Although there is no evidence that even one native plant species has been dri- ven to extinction, or even extirpated within a single U.S. state due to IAS (Davis 2003), researchers acknowledge that it may require many years before an estab- lished alien rapidly expands its range and abundance at the expense of local bi- ological communities (Clout & Poorter 2005). This report addresses one potentially IAS, Daphne mezereum, which was re- cently documented in Vilas County, Wisconsin (bordering Michigan Upper Peninsula). Daphne, a shrubby genus of temperate Europe and Asia, is repre- sented by 70 species (Gleason & Cronquist, 1991). Considerable numbers of these, including D. mezereum L., are cultivated for their attractive, fragrant flow- ers, and in some species, evergreen leaves (Bailey Hortorium Staff 1976). D. mezereum is a low-growing (one meter) deciduous shrub that flowers in early spring (March or early April), before the new leaves have expanded, hence the common name from Europe, February Daphne. The precocious flowers arise on tiny branches from the axillary buds of the previous year’s leaves. The stem con- tinues to grow from the terminal bud, such that the brilliant red fruits are below the leafy stems of the current season. The plant is poisonous in all its parts, but human poisoning is mostly traced to ingestion of the fruit and seeds (Lampe & McCann 1985). Exposure to the skin can result in minor and short-lived irritation. Lewis and Elvin-Lewis (2003) state that it is “fatal to humans; burning of throat and stomach, internal bleeding, weakness, coma, and death; the [diterpene] mezerein also carcinogenic in animals.” The specific epithet, mezereum, is from the medieval name Mezereum, de- rived from the Persian Mazariyun, a name given to a species of Daphne (Grieve, n.d.). D. mezereum shares a long history with humans, reported to have been in cultivation in Eurasia since 1561 (Rehder 1940). The plant is well-adapted to 60 THE MICHIGAN BOTANIST Vol. 45

FIGURE 1. Daphne mezereum voucher from OSH (photo by the author) temperate climates—in North America D. mezereum is successfully cultivated within growing zone 3 (–40 to –34°C). D. mezereum has long been present as an escape in New England and adja- cent Canada. It first appears as a garden escape in Gray (1889): “Escaped from cultivation in Canada, Mass., and N. Y.” In the previous edition (Gray 1868), it is only mentioned as being in cultivation, and no comment as to its becoming 2006 THE MICHIGAN BOTANIST 61 naturalized is offered in the Addenda segment, dated January, 1868, where a number of other such “weed reports” are given. Its weedy tendencies are men- tioned in Webb and Ferguson (1968). “ . . . often cultivated for ornament and . . . occasionally naturalized by bird-dispersal.” Indeed, D. mezereum is identi- fied as a “potentially invasive species” in Canada where the plant is established in moist forests of southern Ontario (Havinga, 2000), while presently in the U.S. it is recognized as invasive only in certain regions of Massachusetts (Swearin- gen, 2005). Based on a July 2005 collection by Steve Garske, Education Specialist/Inva- sive Plant Aide, D. mezereum appears naturalized in west central Vilas County and can be included as part of the state flora. A voucher specimen of D. mez- ereum that was donated to OSH represents a state record bearing the accession number 113103 (Figure 1). Duplicate vouchers are housed at UWSP and DUL. Garske discovered the D. mezereum population approximately 1.9 km north of the city of Boulder Junction (Boulder Junction Township) during an invasive species survey conducted on behalf of the Great Lakes Indian Fish & Wildlife Commission. The range and township location for the D. mezereum site is R7E, 1 1 T42N, SE ⁄4 SE ⁄4 Section 8, while the latitude/longitude coordinates are 46E 07′ 50″ N, 89E 38′ 30″ W (WGS84). According to Garske (Personal email communication, 16 February 2006), the population is established outside cultivation, occupying an area of approxi- mately 320 m2 beneath disturbed, regenerating aspen forest. Seedlings are re- ported abundant, especially below mature plants beneath a canopy shading 60- 80% of the groundlayer. Garske explained that a Boulder Junction resident informed him that in the early 1900s a local man who was a “horticulturalist” imported “all kinds of things to grow” near the plant collection site. In fact, Garske was shown a plant of D. mezereum on the man’s lake house property, which presumably is de- scended from the original planting done there in the early 1900s. Garske specu- lates that the patch he discovered nearby may possibly have been introduced and since spread, appearing naturalized as a small isolated copse. Given the IAS potential of D. mezereum, Garske recommends (and this au- thor concurs) that the naturalized patch of D. mezereum, as well as other IAS present at the site, Lonicera × bella and Veronica chamaedrys, be eradicated sooner rather than later. Apart from prevention, which isn’t an option in this cir- cumstance, a modest eradication effort may be the next best method for aiding protection of the integrity of the local Boulder Junction flora in Vilas County.

LITERATURE CITED Bailey Hortorium Staff. 1976. Hortus Third. Macmillan Publishing Co., Inc., New York. Clout, M. N. & M. Poorter. 2005. International Initiatives Against Invasive Alien Species. Weed Technology, 19:523–527. Davis, M. A. 2003. Biotic Globalization: Does competition from introduced species threaten biodi- versity? BioScience, 53(5)483-489. Elton, C. S. 2000. The Ecology of Invasions by Animals and Plants. University of Chicago Press, Chicago, Illinois. 62 THE MICHIGAN BOTANIST Vol. 45

Gleason, H. A. & A. Cronquist. (1991). Manual of Vascular Plants of Northeastern United States and Adjacent Canada. New York Botanical Garden, Bronx, NY. Gray, A. 1868. Manual of the Botany of the Northern United States, edition 5, eighth issue. Ivison, Blakeman, Taylor & Co., New York and Chicago. Gray, A. 1889. Manual of the Botany of the Northern United States, edition 6 (revised and extended by Sereno Watson and John Merle Coulter). American Book Company, N. Y. etc. Grieve, M. (n.d.). Mezereon. Retrieved Feb. 16, 2006, from Botanical.com Web site: http://www. botanical.com/botanical/mgmh/m/mezere34.html. Havinga, D (and the Ontario Invasive Plants Working Group). 2000. Sustaining Biodiversity (A Strategic Plant for Managing Invasive Species in Southern Ontario. Office of the City Forester, City of Toronto, Parks and Recreation, 21st Floor. East Tower, City Hall M5H 2N2 Lampe, K. F. & McCann, M. A. 1985. AMA Handbook of Poisonous and Injurious Plants. American Medical Association, Chicago, Illinois. Lewis, W. & M. P. F. Elvin-Lewis. 2003. Medical Botany; Plants Affecting Human Health, edition 2. John Wiley & Sons, Inc., Hoboken, New Jersey. Rehder, A. 1940. Manual of Cultivated Trees and Shrubs. 2nd edition. Verbatim reprint, Dioscorides Press, Portland, Oregon, 1986. Swearingen, J. 2005. Alien Plant Invaders of Natural Areas. Plant Conservation Alliance, Alien Plant Working Group. USDA. (n.d.). Plants profile. Retrieved 16 February 2006 from Plants Database Web site: http://plants.usda.gov/java/profile?symbol=DAME3 Webb, D. A. & I. K. Ferguson. 1968. Daphne (Thymelaeaceae) in Flora Europaea 2: 257. Cambridge University Press. Wilcove D. S., D. Rothstein, J. Dubow, A. Phillips & E. Losos E. 1998. Quantifying threats to im- periled species in the United States. BioScience, 48: 607–615. Wilson, E. O. 1992. The Diversity of Life. Belknap Press, Cambridge, Massachusetts