| callus | a mass of thin-walled cells, usually developed as the result of wounding or infection. |
| caltrop | an herb with spiny pods; I.e., puncturevine |
| calyx | the outer set of perianth segments or floral envelope of a flower, usually green in color and smaller than the inner set. |
| cambium | A one- or two-celled layer between the phloem and xylem that produces both these tissues and results in diameter growth. |
| canes | a long woody pliable stem rising from the ground. |
| canker | a necrotic, often sunken lesion on a stem, branch, or twig of a plant. |
| cast skins | the outer layer of an exoskeleton shed by an insect or mite and seen on leaves or twigs. |
| castings | fecal material; caterpillar pellets. |
| caterpillar | in general, the larvae of Lepidoptera; in Hymenoptera, the larva of the saw-flies. |
| chlorosis | of plants, fading of the color of the chlorophyll of plant leaves, caused by environmental stress, chemical deficiency, disease, insects, or mites. |
| chlorotic | of plants, fading of the color of the chlorophyll of plant leaves, caused by environmental stress, chemical deficiency, disease, insects, or mites. |
| cocoon | a covering, composed partly or wholly of silk or other viscid fiber, spun or constructed by many larvae as a protection to the pupa. |
| crawlers | the first stage (nymph) out of the egg of certain plant lice (scales, adelgids, etc.). This stage is quite mobile, while subsequent nymphal stages are stationary. |
| cultivars | an organism of a kind (as a variety, strain, or race) that has originated and persisted under cultivation. |
| cultivated | maintained by humans. |
| cutworms | caterpillar stage of the night flying "millers" or noctuid moths. |