(a) Caliper. For nursery stock trees:

(1) caliper is measured at six inches above soil level; which should be at or near the top of the root flare, and six inches above the root flare for bare root plants, up to and including the four-inch caliper size interval (i.e., from four inches up to, but not including, four and one-half inches);

(2) if the caliper measured at six inches is four and one-half inches or more, the caliper must be measured at 12 inches above the ground level, soil line, or root flare, as appropriate; and

(3) if a tree has multiple stems, caliper is one-half of the combined caliper of the three largest trunks.

(b) Diameter.

(1) Diameter at breast height. Diameter at breast height [“DBH”] is the measurement of a tree trunk at a height of four and one-half feet above the ground, on the uphill side of the tree, or as recommended in the Landscape and Tree Manual for special situations for tree fork, leaning trees, or on slopes.

(2) Multiple stems. For trees with multiple stems, the diameter of the trunk is measured at the narrowest point below branching when branching occurs below DBH, or near DBH.

(3) Branching. When branching occurs at or lower than 12 inches above the ground, diameter of the trunk includes the diameter of the largest stem plus the average diameter of the remaining stems, measured at DBH.