Virginia, Maryland, and District of Columbia

Abstract

Pleioblastus pygmaeus (Miq.) Nakai (POACEAE)—VIRGINIA, Fairfax County: eastern bank of Dead Run floodplain in mature woodland, approximately 1 km south of George Washington Memorial Parkway, 26 January 2012, Steury 120126.1 (George Washington Memorial Parkway Herbarium, JSU); unnamed tributary 50 m from Potomac River and 4.8 km north of Mt. Vernon, 2 July 2012, Steury 120702.1 (George Washington Memorial Parkway Herbarium, JSU). MARYLAND, Montgomery County: Takoma Park, Sligo Creek Park, eastern bank of Sligo Creek floodplain just downstream of Maple Avenue Bridge, 8 March 2012, Parrish & Steury 120308.1 (George Washington Memorial Parkway Herbarium, JSU, US). DISTRICT OF COLUMBIA: Rock Creek Park at terminus of Juniper Street, NW, on floodplain of Rock Creek and extending up a short slope, 8 March 2012, Parrish & Steury 120308 (George Washington Memorial Parkway Herbarium, JSU). Significance. These are the first records for North America (Kartesz 1999, Barkworth et al. 2007). Pleioblastus pygmaeus (pygmy bamboo) is native to Japan (Honshu, Shikoku, and Kyushu) where it is known only in cultivation (Ohwi 1965, Suzuki 1978) and likely represents a horticultural derivative of Pleioblastus variegatus (Siebold ex Miquel) Makino, or ally in Pleioblastus section Nezasa Koidzumi (Ohrnberger 1999). This species is characterized by elongate rhizomes sprouting solitary, minutely ribbed, purplish culms (drying to gray), to 1.5 m tall and 4 mm in diameter. Nodes bear numerous, tan to brownish, stiff, antrorsely fringed hairs and are typically fastigiate and three branched on mature canes and unbranched on young ones. Foliage leaf blades are green, unvariegated, abruptly acuminate, with wedged to rounded bases and a short pseudopetiole, pubescent on both sides, more densely so abaxially where cross-veins are evident, typically to 1.3 cm wide and 13.5 cm long with two or three lateral veins on each side of the midrib on branched canes and to 2.3 cm wide and 18.3 cm long with four or five veins on each side of the midrib on unbranched canes. Foliage leaf sheaths are glabrous and often bristled at the apex. The only other species in this genus reported from North America (Georgia and Tennessee) is P. simonii (Carriere) Nakai (Duncan & Kartesz 1981, DeSelm et al. 1994). In Virginia, P. pygmaeus was found at two sites, one patch measuring 19.5 m 3 14.7 m in old Liriodendron tulipifera L., Fagus grandifolia Ehrh., Asimina triloba (L.) Dunal. woodland along Dead Run (38857 41.76 N, 77810 24.21 W) and another patch approximately 40 m 3 30 m near the mouth of a small unnamed tributary of the Potomac River 4.8 km north of Mt. Vernon (3884334.08 N, 7780232.18 W). The Maryland population measured 8.4 m3 5.0 m and occurred in woodland with a mixture of native (Acer negundo L., Fraxinus pennsylanica Marshall, Platanus occidentalis L., Ulmus americana L.) and nonnative (Albizia julibrisson Durazz. and Morus alba L.) trees. The colony in the District of Columbia measured 55.0 m 3 16.7 m and occurred in disturbed woodland containing native trees and shrubs such as Acer negundo L., Acer rubrum L., Carpinus caroliniana Walt., Carya cordiformis (Wangenh.) K. Koch, Lin*email address: brent_steury@nps.gov Received November 30, 2012; Accepted February 7, 2013. DOI: 10.2179/12-045