| NAME OF PLANT | WHERE FOUND | DATE | WHERE FOUND | DATE |
| Clinopodium vulgare | ||||
| wild basil | ||||
| Cochlearia anglica | ||||
| English scurvygrass | ||||
| Cochlearia danica | ||||
| Danish scurvygrass | ||||
| Cochlearia officinalis | ||||
| common scurvygrass | ||||
| Coeloglossum viride | ||||
| frog orchid | ||||
| Colchicum autumnale | ||||
| meadow saffron | ||||
| Conium maculatum | ||||
| hemlock | ||||
| Conopodium majus | ||||
| pignut | ||||
| Convallaria majalis | ||||
| lily of the valley | ||||
| Convolvulus arvensis | ||||
| field bindweed | ||||
| Conyza canadensis | ||||
| Canadian fleabane | ||||
| Cornus sanguinea | ||||
| dogwood | ||||
| Cornus suecica | ||||
| dwarf cornel | ||||
| Coronopus didymus | ||||
| lesser swine-cress | ||||
| Coronopus squamatus | ||||
| swine-cress | ||||
| Corylus avellana | ||||
| hazel | ||||
| Cotoneaster horizontalis | ||||
| wall cotoneaster | ||||
| Cotoneaster simonsii | ||||
| Himalayan cotoneaster | ||||
| Crambe maritima | ||||
| sea kale | ||||
| Crassula helmsii | ||||
| New Zealand pigmyweed | ||||
| 23 | ||||