Carex merritt-fernaldii - Castilleja puberula
- Carex merritt-fernaldii
- Carex mertensii
- Carex mesochorea
- Carex meyenii
- Carex michauxiana
- Carex michelii
- Carex microchaeta
- Carex microchaeta ssp. microchaeta
- Carex microchaeta ssp. nesophila
- Carex microdonta
- Carex microglochin
- Carex microptera
- Carex microrhyncha
- Carex misandra
- Carex misera
- Carex missouriensis
- Carex mitchelliana
- Carex molesta
- Carex molestiformis
- Carex montis-eeka
- Carex morrowii
- Carex muehlenbergii
- Carex muehlenbergii var. enervis
- Carex muehlenbergii var. muehlenbergii
- Carex multicaulis
- Carex multicostata
- Carex muricata
- Carex muriculata
- Carex muskingumensis
- Carex nardina
- Carex nardina var. hepburnii
- Carex nardina var. nardina
- Carex nebrascensis
- Carex nelsonii
- Carex nervina
- Carex neurophora
- Carex nigra
- Carex nigricans
- Carex nigromarginata
- Carex normalis
