Carex is a very large genus with ca. 1800 species. It is cosmopolitan but more concentrated in cold holarctic regions. More than 60 species are native in Belgium (see Lambinon & al. 2004) but there are remarkably few non-native species. In the present treatment non-native representatives of the genus are therefore opposed against closely related and/or more or less similar native species (or at least occurring in the territory covered by the Flora of Lambinon & al. l.c.). An illustrated overview of alien Carices in Belgium was published by Verloove (2016).
Several of our native species are increasingly cultivated as ornamentals and therefore sometimes occur in places where they are definitely non-native. Carex pendula Huds., for instance, is much grown in private as well as public gardens and frequently escapes, even in urban areas (cracks in pavement,…).
Additional aliens: Carex crus-corvi Shutllw. (syn.: C. bayardii Fernald) (N-Am., wool alien) and C. morrowii Boott (temp. As., garden escape).
section Ovales Kunth
Section Ovales comprises numerous very similar species and is particularly well represented in North America. The only western European taxon, Carex ovalis Good., is a locally common native species in Belgium. An increasing number of New World representatives of section Ovales has been discovered in recent times in various parts of Europe, including Belgium. Some of these taxa, although not (yet) recognized in Belgium, might pass unrecorded due to confusion with native Carex ovalis. More or less atypical plants of the latter from unusual or man-made habitats should therefore be studied carefully. Carex bebbii (L.H. Bailey) Olney ex Fernald (syn.: C. tribuloides Wahlenb. var. bebbii L.H. Bailey) is known from Nordtirol, Austria (Wallnöfer 1993) and the Netherlands (J. Koopman, pers. comm.). In Scandinavia (especially Sweden) the following additional taxa have recently been reported: Carex brevior (Dewey) Mack. ex Lunell (syn.: C. straminea Willd. ex Schkuhr var. brevior Dewey), C. straminea Willd. ex Schkuhr (syn.: C. richii (Fernald) Mack.) and C. tribuloides Wahlenb. var. tribuloides (Karlsson 1997, Ericsson 1999, Karlsson 2003). A very helpful and up-to-date overview of this group in Europe was provided by Wallnöfer & Essl (2016).
The phylogeny and classification of the section Ovales was recently revised by Hipp & al. (2006).
1. Female glumes in the middle portion of the spike longer than the mature utricle (native) === Carex ovalis
1. Female glumes in the middle portion of the spike shorter than the mature utricle === 2
2. Mature utricle at least 2 mm wide, 6-9 mm long. Vegetative culms conspicuous, with spreading leaf blades evenly along stem, fertile culms with 7-12 leaf blades. Inflorescence 50-90 mm long, with distinct lowermost spikes. Spikes 12-28 mm long === C. muskingumensis
2. Mature utricle less than 2 mm wide, 3,4-6,8 mm long. Vegetative culms with few leaves clustered, fertile culms with 3-5 leaf blades. Inflorescence 15-60 mm long, usually densely congested. Spikes 7-16 mm long === 3
3. Mature utricle 0,9-1,3 mm wide, 3,4-4,1 mm long. Achene 0,6-0,8 mm wide === Carex crawfordii
3. Mature utricle 1,2-2 mm wide, 4,2-6,8 mm long. Achene 0,7-0,9 mm wide === C. scoparia
Section Paludosae G. Don (sensu Ball & Reznicek 2002)
This section accommodates about 35 species, four of which occur in Belgium: native Carex acutiformis, C. lasiocarpa and C. riparia (Lambinon & Verloove 2012) and alien C. melanostachya. The limits of this section are in need of a worldwide revision. Carex acutiformis differs somewhat from all the other species in having flattened-trigonous, thin-walled utricles, and some authors restrict the section to that species only (e.g. Egorova 1999). Many authors also exclude the usually smaller species with hairy utricles.
1 Utricles hairy (native) === Carex lasiocarpa
Utricles glabrous == 2
2 Utricles at maturity with veins impressed. Sheaths shortly pubescent. Culms slender, 30-50 cm. Leaves 2-4 mm wide. Female spikes 10-20 x 5-7 mm === C. melanostachya
Utricles with veins not impressed at maturity. Sheaths glabrous. Culms coarse, 50-120 cm. Leaves 6-17 (-20) mm wide. Female spikes (30-) 40-100 (-130) x 6-12 mm === 3
3 Utricles 4-5 mm long, very thin-walled and finely papillose, basally more or less trigonous and flattened towards apex, beak emarginate. Female glumes acute to acuminate, usually slightly shorter than ripe utricle. Female spikes 6-8 mm wide, (30-) 60-80 mm long. Male spikes: 2-3. Leaves 6-10 (-17) mm wide. Ligule acute, 5-15 mm long. Lowermost sheaths decaying into reticulate fibres (native) === C. acutiformis
Utricles 5-7 mm long, thick-walled (more or less leathery), not papillose, ovoid and inflated (hardly compressed towards apex), beak 2-fid. Female glumes exceeding utricles, acuminate to aristate. Female spikes 8-12 mm wide, 40-100 (- 130) mm long. Male spikes: (2-) 3-5. Leaves 7-17 (-20) mm wide. Ligule rounded to truncate at apex, 5-10 mm long. Lowermost sheaths splitting into fibres (native) === C. riparia
section Phaestoglochin Dum.
Section Phaestoglochin comprises the taxonomically complex Carex muricata-group. Of this species complex Carex divulsa Stokes, C. muricata L. subsp. lamprocarpa Celak. and C. spicata Huds. are considered to be native. A fourth taxon, Carex muricata subsp. muricata, was recently recorded as an alien. All can be identified with the identification key beneath.
1. Ligule considerably longer than wide. Utricles 5-6 mm long, thickened at base (native) === Carex spicata
1. Ligules at most as long as wide. Utricles less than 5 mm long, not thickened at base === 2
2. Inflorescence (3-) 5-15 cm long, usually lax, the lowermost spikes usually distant. Utricles 4-5 mm long (native) === C. divulsa
2. Inflorescence up to 3 cm long, dense, the lowermost spikes not very distant. Utricles 3-4,5 mm long === 3
3. Utricles (3,5-) 4-4,5 mm long, strongly patent. Female glumes blackish or dark reddish-brown, darker and shorter than the utricles === C. muricata subsp. muricata
3. Utricles 3-3,5 mm long, erecto-patent. Female glumes pale brown, similar in colour to paler than and almost as long as the utricles (native) === C. muricata subsp. lamprocarpa
section Multiflorae (J. Carey) G. Kükenthal
This section is obviously most closely related to section Vulpinae (Heuffel) H. Christ (see also Ball & Reznicek 2002). A North American species, Carex vulpinoidea, is fairly reminiscent of the Belgian natives Carex cuprina (Sándor ex Heuffel) Nendtvich ex A. Kerner and C. vulpina L.; it is easily distinguished in the following couplet.
- Leaf sheaths transversally rugose (ribbed). Utricles 2-3 mm long, patent at maturity. Inflorescence up to 10 cm long, dense and more or less lobed but the lowermost spikes distant === Carex vulpinoidea
- Leaf sheaths not rugose. Utricles 4-6 mm long, erecto-patent at maturity. Inflorescence rarely exceeding 7 cm (native) === C. cuprina and C. vulpina
section Secalinae (O.F. Lang) Kük.
Section Secalinae is rather characteristic and accommodates only few species (three according to Egorova 1999), including Carex hordeistichos Vill. and C. secalina. The former is native in northern France, close to the Belgian borders (Lambinon & al. 2004). Carex secalina would key out to this but is distinguished as follows:
- Utricles 5-7 mm long, not in distinct rows, surface glabrous. Leaves 2-3 mm wide === Carex secalina
- Utricles 8-12 mm long, in distinct rows, surface sparcely pubescent. Leaves 3-5 mm wide === C. hordeistichos
section Lupulinae Tuckerman ex J. Carey
This section with six closely related species from eastern North America is unmistakable. Its members have the largest perygynia of the entire genus (see also Ball & Reznicek 2002). The inflorescence spikes most closely resemble those of Sparganium. At least two species are increasingly cultivated as ornamentals and have been reported as escapes in Europe: Carex grayi and C. intumescens Rudge (Mossberg & Stenberg 2010, Koopman 2011). The former was recently also found as an escape from cultivation in Belgium.
Ball P.W. & Reznicek A.A. (2002) Carex. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 23. Oxford University Press, New York-Oxford: 254-572.
Chater A.O. (1980) Carex. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 5. Cambridge University Press, Cambridge: 290-323.
Egorova T.V. (1999) The sedges (Carex L.) of Russia and adjacent states (within the limits of the former USSR). St.-Petersburg, St.-Petersburg Chemical-Pharmaceutical Academy – Saint-Louis, Missouri Botanical Garden Press: 772 p.
Ericsson S. (1999) Kanadaråg Leymus innovatus och andra amerikaner. Svensk Bot. Tidskr. 93: 195-200.
Hipp A.L., Reznicek A.A., Rothrock P.E. & Weber J.A. (2006) Phylogeny and classification of Carex section Ovales (Cyperaceae). Int. J. Plant Sc. 167(5): 1029-1048.
Karlsson T. (1997) Förteckning över svenska kärlväxter. Svensk Bot. Tidskr. 91: 241-560.
Karlsson T. (2003) Nyheter i den svenska kärlväxtfloran IV. Enhjärtbladiga växter. Svensk Bot. Tidskr. 97: 179-197.
Koopman J. (2011) Carex Europaea: Carex L. (Cyperaceae) in Europe. 1. Accepted names, hybrids, synonyms, distribution, chromosome numbers. Margraf Publishers, Weikersheim.
Kooman J. (2015) Allochtone Zeggen (Carex-soorten) in Nederland. Gorteria 37: 73-83.
Kükenthal G. (1909) Cyperaceae - Caricoideae. In: Engler H.G.A. (ed.), Das Pflanzenreich 38: 1-824.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Mossberg B. & Stenberg L. (2010) Den nya nordiska Floran. Bonnier Fakta, Stockholm: 928 p.
Řepka R., Lustyk P. & Trávníček B. (1997) Carex scoparia – a new alien sedge in Europe. Preslia 69: 161-168.
The Global Carex Group (2016) Megaphylogenetic Specimen-Level Approaches to the Carex (Cyperaceae) Phylogeny Using ITS, ETS, and matK Sequences: Implications for Classification. Syst. Bot. 41(3): 500-518. [available online at: http://www.bioone.org/doi/pdf/10.1600/036364416X692497]
Verloove F. (2016) Adventieve en ingeburgerde zeggen (Carex, Cyperaceae) in België. Dumortiera 108: 13-21. [available online at: http://www.br.fgov.be/DUMORTIERA/DUM_108/Dum_108_13-21_Carex%20exoten_Ve...
Wallnöfer B. (1993) Carex bebbii und Carex vulpinoidea, zwei eingeschleppte Arten aus Nordamerika, sowie 8 weitere Gefässpflanzen Nordtirols (Österreich). Linzer biol. Beitr. 25: 397-409.
Wallnöfer B. & Essl F. (2016) Overview on alien Carex species of section Cyperoideae (including Ovales) in Europe and the discovery of Carex scoparia in Austria. Annalen des Naturhistorischen Museums in Wien, Serie B, 118: 115-127.