Much like no. 16 [Juncus pylaei Laharpe], but with very dense and head-like infl mostly 1.5-2.5 נ1-1.5 cm; invol lf 5-15 cm; tep a little looser, the outer as long as the inner; fr usually mucronate; basal sheaths usually rather pale brown; stem avg with more numerous (up to 25 or even 30) ridges; fr truncate, apiculate; 2n=42. Low, marshy or boggy or peaty places; native of Europe, locally intr. from Nf. and N.S. to N.Y. and Que. (J. effusus var. c.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
