THIS GENERALLY APPLIES TO ALL PALMS
American Association of Nurseryman, Inc., Approved 1990 – American National Standards Institute, Inc.
In size grading palm trees, height shall take precedence. Either of two heights may be specified: overall height or trunk height. Overall height is the perpendicular height from the ground to the top of the arc made by the uppermost arching frond with the tree standing in natural position. Trunk height is measured from the ground line to the base of the heart leaf.
(Taken from 1990 edition of the American Standard for Nursery Stock, page 4.)