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Viburnum sieboldii Miq. Adoxaceae Siebold’s Arrowwood.

Significance of the Report. First known naturalized occurrence in Michigan of a potentially invasive species.

Previous Knowledge. Viburnum sieboldii is a large shrub or small tree native to Japan, where it occurs in thickets in lowlands and low mountains (Ohwi 1965). It was introduced to eastern North America in the late nineteenth century as a landscape ornamental, and is known to escape occasionally from cultivation in its introduced range (Kunstler 1993, Gleason and Cronquist 1991). Prior to this collection, naturalized populations of V. sieboldii were known in North America primarily from the Mid-Atlantic region of the United States, from Vir- ginia north to New York and Massachusetts (USDA NRCS 2014), although more recently it has also been reported from eastern and southern Ohio (Vincent et al. 2011). Escaped populations are known to establish in a variety of habitats, in- cluding mesic forests, stream edges, and suburban parks, and have been reported as abundant or invasive in New Jersey, New York, and Pennsylvania (Kunstler 1993, DeCandido and Lamont 2004, Pennsylvania Department of Conservation and Natural Resources 2014, Central New Jersey Invasive Species Strike Team 2014). On the other hand, Widrlechner and Iles (2002) found that V. sieboldii was at relatively low risk of naturalizing in Iowa because of climatic differences between there and the native habitat of V. sieboldii in Japan. However, it is un- known whether or how ornamental cultivars may differ from native genotypes in invasive potential. The genus Viburnum was long included in the Caprifoliaceae, but is now considered to belong to the Adoxaceae.

Discussion. This collection represents the first known naturalized occurrence of V. sieboldii in Michigan or elsewhere in North America outside the Mid-At- lantic states and Ohio. In addition to this occurrence in Kent County, a second population of several individuals was observed and photographed by Sue Tepatti in 2012 (S. Tepatti, pers. comm.) in a floodplain forest along the Rouge River near Inkster in Wayne County, Michigan. Given the evidence from the Mid-At- lantic region of the ability of V. sieboldii to become invasive, the presence of nat- uralized populations in Michigan raises concerns about the potential spread and impact of the species on native plant communities. As a precaution, land man- agers and others should consider including V. sieboldii in statewide early-detec- tion and rapid-response efforts for invasive species.

Diagnostic Characters. Viburnum sieboldii is a shrub or small tree with op- posite branching and simple, unlobed, ovate to obovate leaves with simple or forked lateral veins that each extend to a tooth (Figure 1; Gleason and Cronquist


FIGURE 1. Viburnum sieboldii at Blandford Nature Center, Kent County, Michi- gan.

1991). The deciduous leaves have a prominent foul odor when crushed, readily distinguishing V. sieboldii from other species of Viburnum with unlobed leaves. In spring and early summer, it bears many small white flowers in cymes, which are often abundant in ornamental cultivars. Red drupes are formed in late sum- mer and turn blue-black in the fall. Neither flowers nor fruits were observed in the Michigan populations.

Specimen Citation. Kent County: Blandford Nature Center, Grand Rapids, Michigan. On August 18, four individuals were observed in the understory of a mesic forest. Associated species: Acer saccharum, Fagus grandifolia, Fraxinus americana, Lindera benzoin, Carex blanda, and Toxicodendron radicans. Hes- linga 12 (MICH).


Carex squarrosa L. Cyperaceae Squarrose sedge.

Significance of the Report. Significant range extension of a species with critically imperiled status in Michigan.

Previous Knowledge. Carex squarrosa is a clumped sedge of moist woods, wet depressions, and ditches, including disturbed and successional habitats (Michigan Natural Features Inventory 2007; Voss and Reznicek 2012). Carex squarrosa is a native of North America, the known range of which extends from the Great Plains east to Rhode Island and Virginia, and from Georgia and Louisiana north to Michigan, Minnesota, and Ontario (USDA NRCS 2014). De- spite the broad geographic distribution of the species, C. squarrosa is uncom- mon throughout much of its range (e.g., Graves et al. 1910; Michigan Natural Features Inventory 2007; New York Flora Association 2014). Prior to this col- lection, the known distribution of C. squarrosa in Michigan was restricted to Lenawee, Monroe, Oakland, St. Clair, Washtenaw, and Wayne Counties in the southeast corner of the state (Voss and Reznicek 2012), with the exception of a dubious historical record from 1888 in Keweenaw County (Herman 1951). The nearest record relative to this Berrien County occurrence is from Porter County in northwest Indiana, at least 25 miles away (USDA, NRCS 2014).

Discussion. Although globally, C. squarrosa is considered apparently secure (G4) to secure (G5), it is listed as critically imperiled (S1) in Michigan and as a species of special concern (Michigan Natural Features Inventory 2007). This oc- currence fills a gap in our knowledge of the geographic distribution of the species and substantiates our understanding of its habitat requirements, specifi- cally its ability to persist in relatively open successional habitats. Also, the isola- tion of this occurrence of C. squarrosa relative to others raises interesting ques- tions on the metapopulation and dispersal ecology of uncommon species in disjunct populations. For example, if C. squarrosa is able to occupy a variety of forested and early successional habitats but remains uncommon throughout its range, is dispersal the most important limiting factor in the establishment of C. squarrosa, as is the case with several other Carex species (Velland et al. 2000)? If so, what is the primary dispersal mechanism of C. squarrosa and related sedges? What is the rate of genetic exchange between disjunct populations of C. squarrosa? How, if at all, do the answers to these questions influence future con- servation efforts of C. squarrosa and other rare species?

Diagnostic Characters. Carex squarrosa is a clumped sedge with leaves 3-6 mm wide and with erect, ovoid spikes with numerous spreading perigynia (Fig- ure 2). Spikes are typically solitary on each stem and staminate on the lower por- tion only (Gleason and Cronquist 1991). The slightly inflated perigynia contain a narrowly ellipsoid achene that is a little more than twice as long as wide and that has a persistent, strongly sinuous style. In contrast, the closely-related C. ty- phina (once considered to be a variety of C. squarrosa [C. squarrosa L. var. ty- phina (Michx.) Nutt.]) has achenes that are less than twice as long as wide and straight or slightly bent styles (Gleason and Cronquist 1991, Voss and Reznicek 2012).


FIGURE 2. Carex squarrosa at Chikaming Township Park and Preserve, Berrien County, Michigan.

Specimen Citation. Berrien County: Chikaming Township Park and Pre- serve, 1.3 miles east of Lakeside, Michigan, 0.1 miles southeast of the crossing of Warren Woods Road and I-94. On August 28, 2012, several fruiting individu- als were observed in a canopy opening within an early-successional wet-mesic


forest. Associated species: Fraxinus pensylvanica, Toxicodendron radicans, Ag- rimonia parviflora, Fragaria virginiana, Juncus effusus, Solidago rugosa, and Rosa multiflora. Heslinga 13 (MICH).


I would like to thank Scott Namestnik and Tony Reznicek for assistance with and confirmation

of the identification of Viburnum sieboldii. Cardno JFNew allowed me time to work on this report,

and Michael Huft and anonymous reviewers provided comments that led to its improvement.


Central Jersey Invasive Species Strike Team (2014). Invasive plant fact sheet: Siebold’s viburnum (Viburnum sieboldii). Available at Invasive%20Plants%20Fact%20Sheet.pdf (Accessed 25 Mar 2014).

DeCandido, R. and E. E. Lamont (2004). The historical and extant vascular flora of Pelham Bay Park, Bronx County, New York 1947–1998. Journal of the Torrey Botanical Society 131: 368–386.

Gleason, H. A. and A. Cronquist (1991). Manual of vascular plants of northeastern United States and adjacent Canada, 2nd edition. The New York Botanical Garden Press, Bronx, New York.

Graves, C. B., E. H.Eames, C. H. Bissell, L. Andrews, E. G. Harger, and C. A. Weatherby (1910). Catalogue of the flowering plants and ferns of Connecticut growing without cultivation. Con- necticut Geological and Natural History Survey, Hartford.

Hermann, F. J. (1951). Additions to the genus Carex in Michigan. American Midland Naturalist 46:482–492.

Kunstler, D. S. (1993). Siebold’s viburnum, Viburnum sieboldii Miquel, new non-native species record for New York. Bulletin of the Torrey Botanical Club 20: 188–190.

M i c h i g a n N a t u r a l F e a t u r e s I n v e n t o r y ( 2 0 0 7 ) . R a r e s p e c i e s e x p l o r e r. Av a i l a b l e a t (Accessed 25 Mar 2014).

New York Flora Association (2014). New York Flora Atlas: Carex squarrosa. Available at (Accessed 25 Mar 2014).

Ohwi, J. (1965). Flora of Japan (In English): A combined much revised and extended translation by the author of his ‘Flora of Japan’ (1953) and ‘Flora of Japan, Pteridophyta’ (1957). Smithsonian Institution, Washington, D.C.

Pennsylvania Department of Conservation and Natural Resources (2014). Invasive exotic plant tuto- rial for land managers. Available at document/dcnr_010227.pdf (Accessed 25 Mar 2014).

USDA, NRCS (2014). The PLANTS Database. National Plant Data Center, Baton Rouge, Louisiana. Available at (Accessed 25 Mar 2014).

Velland, M., M. J. Lechowicz, and M. J. Waterway (2000). Germination and establishment of forest sedges (Carex, Cyperaceae): tests for home-site advantage and effects of leaf litter. American Jour- nal of Botany 87: 1517–1525.

Vincent, M. A., R. L. Gardner, and B. P. Riley (2011) Additions to and interesting records for the Ohio vascular flora (with one new record for Indiana). Phytoneuron 2011–60: 1–23.

——Justin L. Heslinga Land Conservancy of West Michigan 400 Ann St. NW, Suite 102 Grand Rapids, MI 49504