I could use some help with the Trunk Appraisal Formula.

The trunk diameter of a 4" caliper replacement tree is measured at 6" above ground according to American Nursery standards.

Where is the trunk diameter of the existing, appraised tree measured?

Is it 4.5 feet above ground for all trees over 4" caliper

or is it 4.5 feet above ground for trees 8" caliper and greater and 12" above ground for trees 4" to 8" caliper

OR should the appraised trees all be measured at 6" above ground like the 4" caliper replacement tree?

Please email your reply to davie@charter.net if you can help me with this. I would love to hear another opinion and any references.

Our arborist is using the 4.5 feet above ground measurement for appraised trees of 4" caliper or greater, but I am reading different interpretations on the web.

The CTLA Guide follows the ANSI Z60 standareds for measurement. Nursery trees are measured at 6” above ground for trees up to 6” caliper, and at 12” Above ground for trees 6” to 12” in caliper. Landscape trees are usually measured at the prevailing standard height, most often “diameter at breast height”, DBH. This can vary, but most commonly it is 4.5’ above ground.

For your purposes, the original tree should be measured at 4.5 feet, if it is larger than 12” at 12” above the ground. The Replacement Tree is measured by nursery standards, at 6” above ground.

Russ, looking at p. 36 of the 9th Ed. that is measured at 6" above ground for trees <= 4". I think you typed 6" in error. The Guide cites ANSI Z60.1 (1996) but the standard is the same in the new 2004 edition.

You note that a tree larger than 12" would be measured at BH as non-replaceable. I think some of the Regional Plant Appraisal Committees set that threshold as low as 8" so an appraiser should be familiar with regional guidance.

The real test is if an appraised tree is replaceable with available nursery stock in the region. If replacement stock is available the appraised tree and replacment tree should probably be measured at the same height.

And we are faced with some grauy areas in these transition zones. Once you get above the 12: threshold, as you suggest, it's pretty clear the appraised tree is measured at BH.

Scott Cullen