Over the past fifteen years, emerald tussocks of Berkeley sedge have been so successfully established in West Coast gardens that many gardeners have affirmed its horticultural virtues and its role in helping connect their gardens to their native contexts. As a rapidly growing, nearly evergreen perennial for sun or shade, wet or dry soils, Berkeley sedge also tolerates trampling, and reproduces readily from seed in many gardens—all traits sought after in natives for gardens or wildland revegetation, but despised in alien weeds.
As the horticultural renown of Berkeley sedge grew, so did doubt about its species assignment to Carex tumulicola and provenance as a West Coast native. My suspicions arose over a decade ago after my attempts to confirm identity of some nursery stock did not lead to C. tumulicola, or to any other North American sedge. Others reached the same perplexing conclusion independently. Although the name Berkeley sedge presupposes that mother stock was obtained from native populations in the vicinity of Berkeley, California, none of the plants sold as Berkeley sedge exhibit the combination of character states listed for foothill sedge (C. tumulicola) in the regional floras that include any portion of its native range from British Columbia to Southern California.
During 2005, Rick Darke, known for his work with ornamental grasses, graciously arranged to have Dr Tony Reznicek of the University of Michigan Herbarium examine fresh Berkeley sedge material from California. Dr Reznicek is a Carex expert and author of Carex treatments for the new multi-volume Flora of North America North of Mexico. In late November, 2005, Dr Reznicek provided his determination that Berkeley sedge is actually C. divulsa, first described in 1787 from the British Isles, where it is known as grey sedge or grassland sedge, not synonymous with Gray’s sedge (C. grayi) nor gray sedge (C. grisea), both of eastern North America. Grey sedge (C. divulsa) is native from Europe and North Africa east to Central Asia. Naturalized stands are known from Canada (Ontario), United States (Pennsylvania, Mary-land, Missouri, California), Argentina, Australia, and New Zealand.
Carex divulsa and C. tumulicola are members of Carex section Phaestoglochin, a group of twenty-seven temperate Northern Hemisphere species. Both C. divulsa and C. tumulicola produce racemose inflorescences of three to fifteen sessile spikes. The terminal spike is androgynous (two or three staminate flowers distally, pistillate flowers proximally); lateral spikes are androgynous or pistillate. Perigynia are plano-convex, narrowed distally into a bidentate beak through which two stigmata emerge on deciduous styles.
Carex divulsa differs from C. tumulicola in its large, nearly evergreen tussocks; stouter culms; longer, laxer inflorescences with elongated lower internodes and distant lower spikes that deflex at greater than 45o at maturity; longer and wider pistillate scales that remain green to pale brown at maturity; wider perigynia, broadly elliptic in outline, with broader bases; shorter perigynia beaks less than a third of the body length; and shorter anthers. Grey Sedge Cultivars Carex divulsa does not seem to have any named cultivars, but some plant purveyors are selling C. divulsa ‘Kaga-nishiki’ (aka C. ‘Kaga-nishiki’, or C. ‘Gold Fountains’), a cultivar with yellow gold leaf-blade margins. However, ‘Kaga-nishiki’ is a cultivar of C. dolichostachya, a different species from Japan, China, Taiwan, and Philippines.1
The physiological and reproductive traits of grey sedge predispose this species toward becoming a weed of West Coast watercourses and other moist sites. Diligent eradication now of any escaped plants could prevent another pampas grass analogue from invading West Coast wildlands. The name Berkeley sedge should be removed from all wildland revegetation specifications and replaced with foothill sedge (true Carex tumulicola) where appropriate.
Need For Better Plant Identification
The history of how and by whom Berkeley sedge was initially misidentified as Carex tumulicola is now largely unrecoverable. Of greater importance than blame is the recognition that basic plant identification skills are as essential for horticulturists as for botanists. Berkeley sedge provides another example of how some plants are rushed into production and to market before identifications of vouchered specimens have been confirmed by specialists familiar with the plant group involved.
Similar taxonomical problems linger unresolved with some European material of the Deschampsia cespitosa and Festuca cinerea/glauca complexes currently marketed as West Coast natives. More work is necessary to sort out the imposters. In the meantime, as always, caveat emptor.
1 Chater, AO. 1980. Carex L. pp. 290-323 In Tutin, TG; Heywood, VH; Burges, NA; Moore, DM; Valentine, DH; Walters, SM; Webb, DA, (eds.), Flora Europea. Vol 5. Cambridge: Cambridge University Press.
2 Ceska, A; Ceska, O. 2000. Carex tumulicola: an overlooked sedge in British Columbia. Botanical Electronic News 252. https://www.ou.edu/cas/botany-micro/ben/ben252.html.
3 Douglas, GW; Lomer, F; Roemer, H. 1998. New and rediscovered native vascular plant species in British Columbia. The Canadian Field-Naturalist 112: 276-279.
4 Campbell, CA; Reznicek, AA. 1977. New vascular plant records on Pelee and East Sister Islands, Essex County, Ontario. The Canadian Field-Naturalist 92(1): 384-390.
5 Shetler, SG; Stone, S. 2002. Annotated Checklist of the Vascular Plants of the Washington-Baltimore Area, Part II, Monocotyledons. Washington, DC: Smithsonian Institution.
- Griffiths, M. 2000. Japanese sedges. The Garden 125(7): 515. ↩