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Caliper – Synonym for trunk diameter used to measure the size of nursery stock; by convention, measured 15 cm (6 in.) above the ground for stems less then or equal to 10 cm. (4 in.) and at 30 cm. (12 (in.) above ground for stems greater than 10 cm. (4 in.) Contrast with diameter breast height.
Canopy – The part of the crown composed of leaves and small twigs.
Cavity – An open wound, characterized by the presence of decay and resulting in a hollow structure.
Callus – Undifferentiated tissue initially formed by the cambium around and over a wound.
Chlorotic – Foliage that has yellowed due to disease or mineral deficiency.
Circling Roots – Roots that grow around the trunk in a circular manner rather than laterally away from it.
Clay loam – A fine-textured solid that usually breaks into clods or lumps that are hard when dry. When the moist soil is pinched, it will break readily.
Cleaning – Selective pruning to remove dead, diseased and broken branches, and foreign objects.
Codominant – A situation where a tree has two or more stems which are of equal diameter and relative amounts of leaf area. Trees with codominant primary scaffolding stems are inherently weaker than stems, which are of unequal diameter and size.
Compartmentalization – The boundary-setting process that resists loss of normal wood function and resists the spread of discoloration and decay; a process that separates injured or decayed tissue from healthy tissue.
Compression Wood – Type of reaction wood that develops on the underside of branches and leaning trunks in coniferous trees; tends to maintain branch angle of growth or straighten the trunk.
Conk – Fruiting or spore producing body of wood decay fungi, forming on the external surface of branches and trunks.
Crotch Angle – The angle formed at the attachment between two stems.
Crown – The portion of the tree that bears foliage.
Cultivar– A cultivated variety of a plant. A named plant selection from which identical or near-identical plants can be produced, usually by vegetative reproduction or cloning.
