general - root collar diameter - cell grown trees - seedlings and transplants (open) - seedlings and transplants (container) - girth
The Root Collar Diameter is defined as "the diameter of the main stem measured at or within a specified distance from the root collar." The root collar is between the base of the aerial part of the plant and the top of the root system.
The Root Collar Diameter may be specified for Seedlings (especially Cell grown trees) and transplants, particularly where these are used as rootstocks or for forestry purposes.