The nursery industry generally measures the size of the product based on the container size the plant is in. Standard sizes may be 1 gallon, 5 gallon, 15 gallon, 24” box, 36” box 48” box etc. In areas that plants are field grown and the plants are “balled and burlaped” the size of the plant and caliper size will usually be used.
A large heavily advertised nursery with multiple stores in several states quotes their tree prices and sizes by deceptively misleading the customer with a measuring system that can only have been designed to mask how much their trees really cost in comparison to other nurseries.
If you call this nursery and ask for a quote you will get a quote for example for a 36” or 48” “box spec tree” that is actually a 24” box tree. You are not told this is actually a 24” box tree unless you ask and dig deep. They will tell you that their trees are the same size of other nurseries 36” or 48” box trees or whatever size they want to call it. First this is usually not the case. Assuming their tree is large for a 24” box An honest nurseryman will tell you I have a 24” box and the tree is large for the box and maybe tell you it is ready to be moved up to a 36” box.
There are two questions that should be investigated. First are their trees really bigger in the box than everybody else? (We dare
you to compare) and second if they are a lot larger is that a good thing?
If you ask their salesman why do other nurseries move their trees up to larger boxes they will say so they can sell them for more. Sooooo…we are to believe that the rest of the industry; Nurserymen, Architects, specifiers and horticulturist all move there trees and plants to larger sizes only so they can sell them for more money?
A healthy plant is made up of several complex parts, but to be simple you have roots below grade and you have the foliage above grade. They are interrelated. A healthy vigorous root system is important. Most industry experts agree that root-bound plants are not a good thing. Though a large plant in a small container may at first blush appear to be a better deal - in the long run most industry experts will advise against buying root bound plants unless you are bonzai-ing the plant.