Nursery pots - "trade gallons" versus "real" gallons

Bonsai Nut · Jan 30, 2024

bonsailevel:master said:
I was thinking the same thing. Definitely not 3 gallons.

I decided to start a new thread on this subject in the "tools & equipment" forum...

It is a strange fact in the nursery trade that nursery "trade" containers do not contain the volume of soil that is in their name. For example, a "3 gallon" black nursery container contains 2.3 gallons of soil. For reference - these are general sizes of black blow-molded containers:

#1 "trade gallon" container = 0.734 gallons
#2 "trade gallon" container = 1.66 gallons
#3 "trade gallon" container = 2.296 gallons
#5 "trade gallon" container = 3.843 gallons

I have heard all sorts of explanations, but no one has the same story:
(1) That is the "working" volume of the pot - and that if you fill the pot to the absolute brim, you get closer to the named volume.
(2) That is the amount of soil you would need to fill the pot, when you transplant a tree into it.

To make it even more confusing, not all trade pots have the same volumes, and blow-molded (thin) black plastic pots often have different volumes than injection-molded (thick) black plastic pots. Even the same types of pots can have different volumes - as anyone who has ever tried to stack plastic pots from different manufacturers will attest.

One interesting link, which is nice to have around, is the American Horticulture "American Standard for Nursery Stock" ANSI guidelines. However for pot sizes they list such broad ranges as to be irrelevant

And in case you were wondering, #1, #2, #5 pots make just as little sense in metric liters as they do in imperial gallons.

bonsailevel:master · Jan 30, 2024

Bonsai Nut said:
I decided to start a new thread on this subject in the "tools & equipment" forum...

It is a strange fact in the nursery trade that nursery "trade" containers do not contain the volume of soil that is in their name. For example, a "3 gallon" black nursery container contains 2.3 gallons of soil. For reference - these are general sizes of black blow-molded containers:

1 "trade gallon" container = 0.734 gallons
2 "trade gallon" container = 1.66 gallons
3 "trade gallon" container = 2.296 gallons
5 "trade gallon" container = 3.843 gallons

I have heard all sorts of explanations, but no one has the same story:
(1) That is the "working" volume of the pot - and that if you fill the pot to the absolute brim, you get closer to the named volume.
(2) That is the amount of soil you would need to fill the pot, when you transplant a tree into it.

To make it even more confusing, not all trade pots have the same volumes, and blow-molded (thin) black plastic pots often have different volumes than injection-molded (thick) black plastic pots. Even the same types of pots can have different volumes - as anyone who has ever tried to stack plastic pots from different manufacturers will attest.

One interesting link, which is nice to have around, is the American Horticulture "American Standard for Nursery Stock" ANSI guidelines. However for pot sizes they list such broad ranges as to be irrelevant

And in case you were wondering, #1, #2, #5 pots make just as little sense in metric liters as they do in imperial gallons.

Very insightful. Makes sense now. I've always wondered about nursery cans obviously not being 1,2,3,...so on gallons like they list them as. So now we know,...or not, lol!

Cajunrider · Jan 30, 2024

I believe that the only thing that exceeds the level of volume exaggeration of a nursery pot is the Texas ten gallon hat.

Michael P · Jan 30, 2024

As a landscape architect writing plant specifications, this drove me nuts! Plus the fact that many growers up-pot small plants then immediately release them for sale at the price of the larger pot. I finally just called them #1, #2, etc. I also tried to be on site when the plants were delivered so that I could reject any undersized plants before they went into the ground. By the time I retired there was only one landscape contractor I would work with because he would not put up with this stuff.

penumbra · Jan 30, 2024

It is a ploy of marketing. How much does your pound of coffee weigh? I think most are around 13 ounces.

pandacular · Jan 30, 2024

Michael P said:
As a landscape architect writing plant specifications, this drove me nuts! Plus the fact that many growers up-pot small plants then immediately release them for sale at the price of the larger pot. I finally just called them #1, #2, etc. I also tried to be on site when the plants were delivered so that I could reject any undersized plants before they went into the ground. By the time I retired there was only one landscape contractor I would work with because he would not put up with this stuff.

I've definitely seen this sort of thing. Definitely best to get your pick of the litter, as good ones go quick. Of course, the definition of "good ones" may vary for bonsai, depending on what you're looking to do with it.

Wood · Jan 30, 2024

penumbra said:
It is a ploy of marketing. How much does your pound of coffee weigh? I think most are around 13 ounces.

This doesn't make that much sense to me, because the plant you're getting is presumably an indivisible unit. What benefit does a seller receive when they call a 3.8 gallon container "5 gallons"? Wouldn't most consumers just go off of the discrete sizes rather than the amount of actual soil inside the container? Vanity sizing works in clothes because you're flattering a consumer and provides a differentiation between brands, but nursery containers are all standardized...

penumbra · Jan 30, 2024

Wood said:
This doesn't make that much sense to me, because the plant you're getting is presumably an indivisible unit. What benefit does a seller receive when they call a 3.8 gallon container "5 gallons"? Wouldn't most consumers just go off of the discrete sizes rather than the amount of actual soil inside the container? Vanity sizing works in clothes because you're flattering a consumer and provides a differentiation between brands, but nursery containers are all standardized...

As a nurseryman for over 40 years it makes sense from my viewpoint. When you are dealing with thousands of plants you develop some sense of what a one gallon plant of assorted varieties would amount to. Never necessarily approved of it but I never lost sleep over it either.

Wood · Jan 30, 2024

Doesn't really bother me as a consumer either, just never thought about it. I'll just approach it as just a random size number instead of a specific volume of soil in the future

BrightsideB · Jan 30, 2024

Good post @Bonsai Nut

It is confusing.

penumbra · Jan 30, 2024

Just want to add, there is (or was) a true gallon black plastic nursery pot in the industry. It was refereed to as a true gallon pot years ago but last few times I heard them referenced was as 4 quart pots.

Bonsai Nut · Jan 30, 2024

What triggered this post was another thread where someone purchased 3 gallons of pumice... and it was far short of that volume.

ShadyStump · Jan 30, 2024

I remember reading into this some time ago. I found one article that seemed to make a little bit of sense in an off sorta way.

I don't recall exactly, but they said something like: Back in ye oulden tymes, it really was the volume the pot was named for, but most nursery "pots" were actually buckets and cans or the like being repurposed for plants. As the nursery industry grew, and manufacturers began making purposes built nursery pots, the shape evolved to be slightly smaller at the bottom than the top. This mage it easier to get the root ball out in one piece when planting.
So while the height and top width remained the same, the width at the bottom narrowed, reducing the actual volume. But this happened on the heals of the parlance becoming standardized. Hence a 1 gallon pot is actually slightly less than 1 gallon.

That was a while ago, though, and really don't recall any particulars or where I found that article.
You may feel free to assume I'm talking out my ass.

RobGA · Jan 30, 2024

Cajunrider said:
I believe that the only thing that exceeds the level of volume exaggeration of a nursery pot is the Texas ten gallon hat.

And a Texas mile is 5.5 miles everywhere else. I was in Dallas years ago and asked for directions and the guy said “just a couple miles ahead on the left”, 11 miles later we found what we were looking for.

Cajunrider · Jan 30, 2024

RobGA said:
But a Texas mile is minimized. I was in Dallas years ago and asked for directions and the guy said “just a couple miles ahead on the left”, 11 miles later we found what we were looking for.

Texas distance is measure in beer. It takes a case to go the 880 miles on I-10 Texas.

Orion_metalhead · Jan 30, 2024

Michael P said:
As a landscape architect writing plant specifications, this drove me nuts! Plus the fact that many growers up-pot small plants then immediately release them for sale at the price of the larger pot. I finally just called them #1, #2, etc. I also tried to be on site when the plants were delivered so that I could reject any undersized plants before they went into the ground. By the time I retired there was only one landscape contractor I would work with because he would not put up with this stuff.

I often see plant schedules in plans that call for plants to be specific sizes in addition to the pot size.

Wires_Guy_wires · Jan 30, 2024

Gosh, even more deviations of a weird measurement unit. We work in liters here, but now I'm curious whether or not those are truly liters or that we have 'trade liters' as well!

Shibui · Jan 30, 2024

I was surprised to hear the US refer to plant pots by volume. Down here we usually use the diameter of the pot as the designated size so most regular nursery pots are 15cm (6") across the top of the pot. The manufacturers also give a volume for their pots but that's really only of interest to growers who need to know how much soil would be needed for a given number.
The pot diameter gives a pretty good indication of the size of the plant that's likely to be in it I think. Small differences in volume probably don't affect plant growth and health very much.
More recently pot makers have introduced a wider range of pot shapes and shorter 'squat' pots which adds some complexity to the whole system.

Wires_Guy_wires said:
We work in liters here, but now I'm curious whether or not those are truly liters or that we have 'trade liters' as well!

I'll measure some of the pots here to see whether volumes are actual or notional here too.

Michael P said:
Plus the fact that many growers up-pot small plants then immediately release them for sale at the price of the larger pot.

We also get plenty of commercial growers that pot on small plants and immediately sell for the larger size price. I guess from their perspective most of the costs have gone into the pot and additional soil but as a buyer it always seems like paying more for a small plant.

Cajunrider · Jan 31, 2024

Down here the serious nurseries sell trees and shrubs in whole sale quantity using pot size, caliper, height, spread, and quality grade as specifications. Mg friends and I have ordered them that way for whole house landscaping without issues. We never order plants by pot size alone.

Brian Van Fleet · Jan 31, 2024

Shrink-flation. They did the same thing with ice cream a few years ago.

Nursery pots - "trade gallons" versus "real" gallons

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