Epilobium parviflorum along the Niagara River Reconsidered
P. M. Eckel
Res Botanica, a Missouri Botanical Garden Web Site

July 19, 2004

Epilobium parviflorum along the Niagara River Reconsidered


P. M. Eckel, Missouri Botanical Garden


In 2002 I published an article in the NYFA Newsletter on the Eurasian plant Epilobium parviflorum Schreber, Small-flowered Hairy Willow-herb, found along the Niagara River at Lewiston, New York. I had not realized then that this species was arguably new to the flora of New York state as of the 1997 publication date of the recent checklist by Mitchell and Tucker. The species was earlier recorded for Monroe County on the vouchered distribution map printed by the New York Flora Association (NYFA) in 1990.  Presently the species is still not listed on the NYFA website as occurring in New York State, but I am assured this is a technical artefact (Troy Weldy, pers. comm.) and will be corrected in a later version of the website this year. See: http://nyflora.org/atlas/atlas.htm.


In the checklist of the Ontario flora, Epilobium molle Lam. is given as a synonym of E. parviflorum (Morton & Venn 1990). Apparently, the botanist John Torrey also published an identical name, Epilobium molle, to describe what is now Epilobium strictum Muhlenb. ex Sprengel, a native species of swamps.


John Torrey published Epilobium molle Torrey (1843, Vol. 2 p. 233) = E.  strictum from sphagnous swamps in New York State. In the first volume of the Journal of the Torrey Botanical Club (Vol.1(9): 33) E. molle Torr.  was also used for specimens from Morristown and Chatham, New Jersey.


Epilobium molle Lam., however, does not occur as a synonym for Epilobium parviflorum in the North American Synthesis (Kartesz 1999). According to R.  Mitchell (T. Weldy, pers. comm.) in an upcoming version of the New York State flora, Epilobium hirsutum L. will be cited as a synonym of E. parviflorum to indicate that some specimens cited as E. hirsutum are probably E.  parviflorum instead.


Epilobium parviflorum was first recorded by W. Trelease for North America in 1891 from Kings and Queens Counties in New York State, and Hoboken, New Jersey. Subsequently it was reported for Ontario in the counties of Grey, Simcoe and York (Purcell 1976), and counties in Michigan (Voss 1985). The Nature Conservancy in the state of Ohio has published on-line a list of invasive species of which E. parviflorum is one. There are nine counties listed, and all but one appears to be associated with the Cuyahoga River drainage basin.


This willow-herb is probably more widespread in eastern North America than records show, as it does not occur in the keys and descriptions of the major manuals; the only manual I am aware of that treats this species is that of Voss (1985), which was used to identify the Niagara specimens.  Plants ordinarily might key to the common Eurasian Epilobium hirsutum L., Great Hairy Willow-herb, which has conspicuously larger flowers (11-17 mm long) and sessile leaves, the larger leaves clasping the stem about half way around. Epilobium parviflorum, as the epithet suggests, has smaller flowers (at most 10 mm long), and the leaves are subsessile or on tiny stalks in the upper leaves, not at all clasping. The small flowers resemble those of the more common E. ciliatum or E. coloratum, but those two species have a pubescence on the stem that is of minute incurved hairs. The pubescence of E. parviflorum is of long hairs, these or nearly at right angles to the stem.


The extensive distribution of Epilobium parviflorum along the Niagara River in New York State suggests that it has been an unrecognized element for some time. The characteristic right-angled pubescence should be looked for on the stems of small-flowered Willow-herbs in wet shores, ditches and marshes explored by our membership including feeder streams into the Niagara or along the shore of Lakes Erie and Ontario. The Canadian shoreline could also be examined in late summer. It is possible, from personal observation, that this species may also occur in urban settings (back-yard gardens).


With climactic change imposing new limits on the reproductive vigor of native and alien taxa alike, the flora of the Niagara River, famous for its extraordinary regional diversity of plant species, may be unusually susceptible to changes in its flora. Means of dispersal such as along the river abound (Eckel 2002). The Niagara River as a strait, connecting Lakes Erie and Ontario and the interior of the continent at Lake Superior on the west and its outlet into the Atlantic Ocean to the east, may be an unusual venue for biological invasion. Note that all the counties mentioned in recent literature, other than Trelease's early records near the Atlantic, occur either adjacent to the Lakes and major bodies of water adjacent to the lakes. In Michigan the species is reported in the northern counties below the peninsula near the strait between Lakes Huron and Michigan. River invasions, such as in Ohio, may have derived from a Lake source.  Ultimately, as the first records for this species indicate, the source may have come from as yet unrecorded habitats near the Atlantic Ocean at the mouth of the St. Lawrence.


The Niagara River flora is special for a number of reasons, but its peculiar sensitivity to the establishment of weedy species is noteworthy. Perhaps the oldest alien species, the ancestor of the grocery-store Bing Cherry, Prunus avium L., is extensive and apparently old, perhaps dating to colonial times although some early literature emphasizes the sour cherry in early orchards. Alnus glutinosa has attained invasive status along the Niagara River as has been detailed in Clintonia (Eckel 2003). Even the rare native Iris virginica var. shrevei (Eckel 2000) may prove to be unique to the Niagara River in our region, with I. versicolor appearing to prefer inland stations, although further field work is needed to substantiate this. Epilobium parviflorum has perhaps attained this special status, and there may well be other such species along this famous watercourse.


Specimens of Epilobium hirsutum in the Clinton Herbarium of the Buffalo Museum of Science were examined as possibly E. parviflorum instead. All specimens were E. hirsutum except one (collected by R. Zander in 1971). The following are the four representative specimens indicating the present broad north-south distribution of this plant in western New York:  


Cattaraugus Co., Cattaraugus Indian Reservation, swamp along NY Rte. 238. R. Zander. Oct. 27,  1971.


Erie Co., town of Tonawanda, Niagara River just N of South Grand Island Bridge (Interstate 190) shoreline parcel, wet selectively cut Fraxinus pensylvanica woods, shade, year long wet soil, some Ulmus americana. Beach. P. M. Eckel, August 12, 2003.


Erie Co.: Town of Tonawanda, corner of Sheridan and Kenmore Rds., near Two Mile Creek Road, near Interstate 190; old-growth Quercus palustris, Q. bicolor, Acer rubrum; vernal pools; no shrub layer, P. M. Eckel, Sept. 2001.


Niagara Co., town of Lewiston, shore of Niagara River, 3 lots N of N boundary of Artpark, steel slope, covered with Solidago canadensis, S.  graminifolia, Juncus torreyi; sheet seepage constant. P. M. Eckel, Sept. 19, 2001.


Niagara Co., town of Lewiston, upper RR path at mouth of Niagara River gorge (N end) just S of Artpark, calcareous bedrock with extensive shale-sandstone; by path; Salix eriocephala. P. M. Eckel Sept. 23, 2001.




I thank Troy Weldy and Richard Mitchell of the Natural Heritage Program for crucial information.


Eckel, P. M. & J. Bissell. 2000. Iris virginica L., Southern Blue Flag, Restored to the Flora of New York State. Clintonia 15(3): 7.

Eckel, P. M. 2002. Epilobium parviflorum, a rare European introduction along the Niagara River. NYFA Newsletter 13(2):3-5.

Eckel, P. M. 2003. Two problems in Betulaceae along the Niagara River: Alnus glutinosa and Betula cordifolia. Clintonia. 18(4):3-4.

Kartesz, J. T. 1999. A Synonymized Checklist & Atlas with Biological Attributes for the Vasc. Flora of the U.S., Canada, and Greenland. First Ed. In: Kartesz, J. T. & C. A. Meacham. Synthesis of the N. Amer. Flora, Version 1.0, N. Carolina Bot. Garden, Chapel Hill, NC.

Mitchell, Richard S. & Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. New York State Museum Bulletin 490.

New York Flora Association. 1990. Preliminary Vouchered Atlas of New York State Flora. Ed. 1. New York State Museum Intsitute, Albany.

Purcell, Nancy J. 1976. Epilobium parviflorum Schreb. (Onagraceae) established in North America. Rhodora 78:785-787.

Torrey, J. 1843. A Flora of the State of New York, comprising full descriptions of all the indigenous and naturalized plants hitherto discovered in the state; with remarks on their economical and medicinal properties. Vols. 1 & 2 of Natural History of New York. Albany. 

Trelease, W. 1891. A revision of the American species of Epilobium occurring North of Mexico. Report of the Missouri Botanical Garden 22:67-117.

Voss, Edward G. Michigan Flora. 1985. Part II. Dicots (Saururaceae-Cornaceae). Cranbrook Institute of Science Bulletin 59 and University of Michigan Herbarium, Ann Arbor.