Index of plants by genus
| Species | Common Name | Family |
| Calamintha arkansana | Calamint | Lamiaceae |
| Calla palustris | Wild Calla | Araceae |
| Calopogon tuberosus | Grass Pink Orchid | Orchidaceae |
| Caltha palustris | Marsh Marigold | Primulaceae |
| Calycanthus floridus | Carolina Allspice | Calycanthaceae |
| Calystegia sepium | Hedge Bindweed | Convolvulaceae |
| Campanula americana | American Bellflower | Campanulaceae |
| Campanula aparinoides | Marsh Bellflower | Campanulaceae |
| Campanula rotundifolia | Harebell | Campanulaceae |
| Campsis radicans | Trumpetvine | Bignoniaceae |
| Cardamine bulbosa | Bulbous Springcress | Brassicaceae |
| Cardamine douglassii | Purple Springcress | Brassicaceae |
| Carex scoparia | Lance-fruited Oval Sedge | Cyperaceae |
| Carpinus caroliniana | American Hornbeam | Betulaceae |
| Carya cordiformis | Yellowbud Hickory | Juglandaceae |
| Carya glabra | Pignut Hickory | Juglandaceae |
| Carya ovata | Shagbark Hickory | Juglandaceae |
| Castilleja coccinea | Indian Paintbrush | Scrophulariaceae |
| Castilleja sessiflora | Downy Indian Paintbrush | Scrophulariaceae |
| Catalpa speciosa | Catalpa | Bignoniaceae |
| Caulophyllum thalictroides | Blue Cohosh | Berberidaceae |
| Ceanothus americanus | New Jersey Tea | Ranunculaceae |
| Cephalanthus occidentalis | Buttonbush | Rubiaceae |
| Celtis occidentalis | Hackberry | Ulmaceae |
| Cercis canadensis* | Redbud | Leguminosae |
| Chamaedaphne calyculata | Leatherleaf | Ericaceae |
| Cicuta bulbifera | Bulbet-bearing Water Hemlock | Apiaceae |
| Cicuta maculata | Spotted Water Hemlock | Apiaceae |
| Cimicifuga racemosa | Bugbane | Ranunculaceae |
| Circaea lutetiana | Broadleaf Enchanter's Nightshade | Onagraceae |
| Cirsium muticum* | Fen Thistle | Asteraceae |
| Claytonia virginica | Spring Beauty | Portulaceae |
| Clematis occidentalis* | Western Blue Virginsbower | Ranunculaceae |
| Clematis virginiana | Virginsbower | Ranunculaceae |
| Clethra alnifolia | Summersweet | Clethraceae |
| Collinsonia canadensis | Horsebalm | Lamiaceae |
| Comandra umbellata | Bastard Toadflax | Santalaceae |
| Comptonia peregrina | Sweet Fern | Myricaceae |
| Coreopsis palmata | Prairie Coreopsis | Asteraceae |
| Coreopsis tripteris | Tall Coreopsis | Asteraceae |
| Cornus canadensis | Bunchberry | Cornaceae |
| Cornus alternifolia | Pagoda Dogwood | Cornaceae |
| Cornus florida | Flowering Dogwood | Cornaceae |
| Cornus obliqua | Silky Dogwood | Cornaceae |
| Cornus racemosa | Gray Dogwood | Cornaceae |
| Cornus rugosa | Roundleaf Dogwood | Cornaceae |
| Cornus sericea | Red Osier Dogwood | Cornaceae |
| Corylus americana | American Filbert | Betulaceae |
| Craetagus crus-galli | Cockspur Hawthorn | Rosaceae |
| Craetagus mollis | Downy Hawthorn | Rosaceae |
| Cryptotaenia canadensis | Canadian Honewort | Apiaceae |
| Cyperus rivularis | ||
| Cypripedium candidum | White Lady's Slipper | Orchidaceae |
| Cystopteris bulbifera | Bulblet Fern | Dryopteridaceae |
© 2004 Michael Hough