Container size is a measure of the pot, not the tree. Two growers can both sell you a #45 and hand you noticeably different trees. So rather than talk in generalities, here is what the containers on our farm actually produce, measured across our current stock.
| Container | Caliper | Height |
|---|---|---|
| #30 | 1.5" to 2" | 5' to 8' |
| #45 | 2" to 2.5" | 7' to 12' |
| #65 | 3" to 3.5" | 10' to 14' |
| #100 | 4" to 5" | 14' to 16' |
| #200 | 5" to 6" | 15' to 17' |
| #300 | 7" to 8" | 16' to 18' |
How caliper is measured, and where
Caliper is the diameter of the trunk, and where you measure it changes the number. The nursery standard (ANSI Z60.1) measures 6 inches above the ground for trees up to 4 inches in caliper, and 12 inches above the ground for larger trees, because trunks flare at the base and a measurement taken at the soil line flatters every tree. That is how the gauge in the photograph is being used, and it is how our stock is graded. If a specification says "caliper at 12 inches" for a 3 inch tree, say so on the plant list; the same tree can read a quarter inch different between the two heights.
Multi-trunk ornamentals (crape myrtles, vitex, mountain laurel grown as clumps) are not specified by caliper at all. They are specified by height and number of trunks, which is why the ornamental rows on the table above matter less than the height column does.
What "minimum caliper" on a spec sheet means for the container
A specification that says "3 inch caliper minimum" is asking for a tree that measures at least 3.0 inches at the standard height on the day it is inspected. Read that against the table: a #45 tops out around 2.5 inches, so no #45 will pass. A #65 runs 3 to 3.5 inches, so most will, and the ones at the bottom of the range are the ones to walk past when you tag. Order the container size whose range STARTS at or above the minimum, not the one whose range merely reaches it, and you will not be arguing about a quarter inch at the gate.
Where specs go wrong
The gap that catches people out is between #45 and #65. A #45 tops out around 2.5 inches. If the drawing says 3 inch caliper, a #45 will not get you there, and no amount of picking through the row will change that. You need the #65.
Going the other way, a #100 is a serious piece of freight and needs equipment on site to place it. If a 4 inch caliper is not actually required, a #65 plants more easily and establishes faster.
Height and caliper are not locked together
Notice the overlap. A #45 can be anywhere from 7 to 12 feet tall while staying in roughly the same caliper band. Height varies by species and by how the individual tree grew. If the height matters as much as the caliper, that is a good reason to come and tag rather than order to a number.
Not every variety comes in every size
The combinations that actually exist change through the season as stock sells and new blocks come on. Our availability list is generated from the same inventory records we quote from, so it is the authoritative answer on what pairing exists right now. Each variety also has its own page listing the container sizes we grow it in: see every tree we grow.
If you are specifying for a job that is still a way out, the sizes above are a reasonable planning basis. If you are bidding this week, check the list.
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