Co
- Coeloglossum — green orchises
- Coeloglossum viride var. viriscens — long-bract green orchis
- Coeloglossum viride var. viride — bracted orchid
- Collinsia — horsebalms
- Collinsia canadensis — Canada horsebalm, northern horsebalm, stoneroot, richweed
- Collinsia parviflora — bluelips, small blue-eyed Mary
- Collomia — glueseeds
- Collomia linearis — glueseed, narrowleaf collomia
- Comandra — comandras
- Comandra umbellata — bastard toadflax, star toadflax
- Comptonia — sweetferns
- Comptonia peregrina — sweetfern
- Conioselinum — hemlock parsleys
- Conioselinum chinense — hemlock parsley
- Conopholis— squawroots
- Conopholis americana — squawroot
- Conyza — fleabanes
- Conyza canadensis — Canada fleabane, horseweed, butterweed
- Coptis — goldthreads
- Coptis trifolia — goldthread, canker-root, yellow snakeroot
- Corallorrhiza — coralroots
- Corallorrhiza maculata — spotted coralroot
- Corallorrhiza odontorhiza — autumn coralroot
- Corallorrhiza striata — striped coralroot
- Corallorrhiza trifida — early coralroot, pale coralroot, northern coralroot
- Coreopsis — tickseeds
- Coreopsis lanceolata — lanceleaf tickseed, garden coreopsis, long-stalked coreopsis
- Coreopsis tripteris — tall coreopsis
- Corispermum — bugseeds
- Corispermum americanum — American bugseed
- Corispermum hookeri — Hooker's bugseed
- Corispermum pallasii — Pallas' bugseed
- Corispermum villosum — hairy bugseed
- Cornus — dogwoods
- Cornus alternifolia — alternate-leaf dogwood, pagoda dogwood, green osier
- Cornus amomum subsp. amomum — silky dogwood, red willow, swamp dogwood
- Cornus amomum subsp. obliqua
- Cornus canadensis — Canada bunchberry, crackerberry, dwarf cornel
- Cornus drummondii — roughleaf dogwood, Drummond's dogwood
- Cornus florida — eastern flowering dogwood, common white dogwood
- Cornus foemina — stiff dogwood, English dogwood, stiff cornel
- Cornus rugosa — roundleaf dogwood
- Cornus stolonifera — red-osier dogwood
- Corydalis — corydalises
- Corydalis aurea — golden corydalis
- Corydalis flavula — yellow corydalis
- Corydalis sempervirens — pale corydalis
- Corylus — hazelnuts
- Corylus americana — American hazelnut, American filbert
- Corylus cornuta — beaked hazelnut, beaked filbert
Read more about this topic: List Of Canadian Plants By Genus C