- GrowJourney’s Garden Pot Size Table
- Garden Pot Sizes Decoded
- How We Came Up With the Figures For Our Gardening Pot Size Chart
- Summary Bullet Points
- Why are there so many different pot sizes on the market?
- Is pot size a good measure of value for money?
- Are smaller or larger pots better value for money?
- Why are 9cm pots not marketed in litres?
- Are all trees supplied in pots?
- Approximating Plant Pot Sizes
- Calculating Plant Pot Sizes
- Potting Soil Calculator
- How much soil do I need?
- Shipping Container Dimensions
- External Shipping Container Dimensions
- Internal Shipping Container Dimensions
- Shipping Container Weights (Tare Weight, Gross Weight and Payload)
- Cubic Container Capacity
- Shipping Container Structure
- Understanding Nursery Containers – Common Pot Sizes Used In Nurseries
- About Nursery Plants Pots
- What is #1 Pot Size?
- Grade of Nursery Plant Pots
- Understanding Nursery Stock Sizes
GrowJourney’s Garden Pot Size Table
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Are you completely confused by garden pot sizes? You’re not alone!
In this article, Master Gardener and Permaculturist Eliza Holcombe, will help you make sense of the varying (often conflicting) pot sizes and how to determine a garden pot’s true size & volume.
At least 10,000 of my (Eliza’s) brain cells died during the grueling research that brought you this information, so please honor their brave sacrifice by sharing the article with your other gardening friends (they’re guaranteed to have been confused by pot sizes at some point in their gardening careers)!
Also, 8 out of 9 ducks declare this post to be wonderfully engaging in spite of its non-sexy topic, “choosing the right nursery pot sizes for various plants.”
So, you should keep reading regardless of your short attention span’s vigorous objections. No, really! You’ll be missing out on some fine comedy if you behave like a grumpy goose and just to skip to the bullet point summary or to skip to our pot sizes decoded table.
Garden Pot Sizes Decoded
One of the most frequent questions expert gardeners are asked is what size pot is right for a certain plant. If you’ve ever tried to look this information up for yourself, you may have discovered that the search can be complete chaos.
First, you’ll certainly encounter differing opinions on the matter since asking 12 “expert gardeners” means you’ll get at least 13 conflicting replies. However, the most confusing part is sussing out what the advice you received actually means when you set out to brave the spiders hiding in your recycled nursery pot tower or peruse the racks of decorative planters at the local garden center.
Perhaps you’re that extra nutty crafty person planning to drill holes in Uncle Clyde’s old tin bedpan so you can situate it (and the comfy plants you tuck into it) next to the cobalt bottle tree that protects you from haints. Hey, we fully support you! Down with haints!
Okay, as an example, if you’re told to use a 10” diameter pot, does that mean a 10” pot that holds approximately 1.3 gallons of soil, a 10” pot that holds 2 gallons, or a 10” pot that holds 3 gallons? All three are common sizes sold at nurseries and vary in volume capacity based on their other dimensions.
What are trade gallons?
Alrighty, perhaps we should go by soil volume instead and recommend a 1 gallon pot. Do you choose the pots labeled “one gallon” in nurseries that really only hold 0.664 gallons of soil, or should you find a pot that you can literally fit a full gallon of soil into?
Yep, if you ever looked at a “one gallon” nursery perennial and thought it couldn’t possibly be the same size as the milk jug from the grocery, your eyes weren’t playing tricks on you. Turns out there are “gallons” and then there are nursery “trade gallons” which are approximately equal to 0.71 of a regular gallon.
Does this mean the factory is cutting corners on those little plastic pellets for the injection mold machine or are they catering to wholesale growers who want customers to think they’re buying a bigger plant while they sneakily save a buck on potting soil?!?!?!?! Watch out, Washington Post and NYT, the next Pulitzer for a major conspiracy exposé belongs to the GrowJourney blog!
Now that we’re onto the trade gallons scheme, it must mean our predicament has been solved since everyone’s container size recommendations should mean “trade gallon” pots. Whew. That would mean if you’re supposed to use a “five gallon” nursery pot, your plant actually only needs the 3.55 regular gallons of soil that a 5 trade gallon pot should hold… wait… no!
An internet search turned up nursery standard “five gallon” pots that hold 3.55 gallons, 3.68 gallons, 4.16 gallons, 4.97 gallons, or 5.03 gallons. Didn’t all the plastic pot molding corporations get the conspiracy memo? Also, now we still have no clue what size pot to actually use.
How about we turn to an old standby and look at bulletins and fact sheets released by land grant university Cooperative Extension services? After reading nearly two dozen of them from all over the country, I learned that… nobody agrees, even slightly, right down to whether it should be listed by pot volumes or pot diameters.
More University Extension services used volume, but one office might say 1 gallon for peppers while others insist 5 gallons is the minimum. For tomatoes, extension offices recommended anywhere from 1-15 gallons.
For the record, we cannot imagine growing a successful full-sized tomato plant in a 1 gallon pot!
How We Came Up With the Figures For Our Gardening Pot Size Chart
I gathered as much data as I could find, dropped the extreme numbers from both end of the scale, and came up with an average based on our personal experience and the frequency with which experts made a recommendation (if the majority of extension offices swore by a 5 gallon minimum pot for peppers, that’s what we used).
We’ve put the end results into a table for you to use as a resource (below). The table is complete with conversions into just about any volume measurement you might encounter from nurseries, garden centers, your kitchen measuring tools, or found containers that weren’t originally intended for gardening (make sure to drill enough drainage holes).
We recommend focusing on the volume of soil the pot should hold and whether or not we recommend a minimum soil depth (such as at least 10” deep for beets). The rest of the dimensions can match whatever size pot you have on hand.
If your container didn’t come with its volume labeled, you can measure it yourself by filling it within 1-3 inches of the brim with water or potting soil and then using your largest kitchen measuring tools to find out how much it holds. Plus, think of how delighted your housemates or spouse will be when they discover you dumping dirt in the Pyrex measuring bowl they use for pancake batter?
If all this sounds too complicated, don’t worry! When in doubt just get it as close as you can or go a size or two larger. Your plant doesn’t know how to read seed packet instructions and just wants enough room to grow.
Summary Bullet Points
- We include a minimum recommended size for container gardening with all the seeds we send.
- There are no standard pot sizes (it’s chaos), so we have chosen to use: a) volume in pints or gallons (which is how most pots are sold), b) the likely diameter of pots with the correct volume (if you place a ruler across the widest part on top of the pot you get the diameter), and c) the minimum soil depth for plants that are fussy about it (like root veggies).
- If your container has no volume listed, you can figure out the volume by measuring the amount of soil you can put in it using your largest kitchen measuring tools.
- Some pots may have their volume listed in measurements other than US customary units (gallons, etc.) and you can use our easy table or an online converter to figure it out.
- There are many reasons other than aesthetics and saving space to grow in pots. Some examples include mobility (control how much sun your plant gets and keep it away from extreme temperatures), problems with the local soil (salty, polluted, etc.), or being able to grow food out of the reach of critters like deer and rabbits (such as up on a deck or rooftop).
- Plants with top-heavy growth may need to be anchored to keep it from toppling in strong wind.
- “Minimum recommended” size means you should try to use a pot at least that big, so if you can’t find that exact size just get a bigger one. Additionally, it’s possible to grow plants in “too small” pots, but your watering and fertilizing schedule will be much more demanding if you want healthy plants and a great harvest.
- When using pots with large volumes (3+ gallons), it’s a good idea to buy or mix “large container” potting soil which usually contains bulky fillers like composted pine bark or coconut coir. These fillers do not break down quickly, preventing your soil from getting compacted and anaerobic before the season ends. Our favorite pre-made organic potting mix is Black Gold.
- Most commercial “slow release” fertilizers work based on temperature, so in warmer weather it will disappear much faster than the package label claims. We like to use organic liquid fertilizers on a more frequent basis to ensure our containers get what they need. *Note: Growing in pots is different from growing in-ground (your plants’ roots and symbiont microorganisms have limited space from which to source nutrients and water), which is why we don’t recommend using fertilizers for your in-ground plants and instead recommend you focus on building biological soil fertility.
- Oh, and one other important point: you can buy pots, growbags, raised beds, organic fertilizer, and other container gardening necessities on our store here!
If it’s difficult to read the information in our garden pot size table OR you want a printable version of this chart, please to view the original google doc.
We hope this garden pot size guide was helpful!
Sometimes our articles will contain Amazon affiliate product links. These products have been carefully curated by our team. We use them, trust them, and know they work (or in the case of books, know that the information is extremely helpful). GrowJourney may earn a small commission on any sales that are generated via these affiliate links (without any additional cost to you).
Why are there so many different pot sizes on the market?
Nurseries sell plants at different stages of growth. Most are grown in the ground and then transferred into a pot. Thus a 1 year old tree may be transferred into a 9L pot, a 3 year old tree into a 18L pot. Others are transferred from pot to pot, from a 3L to a 9L for example.
Thus a tree may start out in the ground, before being transferred to a 9L and then a 15L, and so on. A nursery may start out with 300 trees and sell 150 bare root, 100 9Ls and 50 15Ls. Although, not all nurseries do this. Thus a tree may remain in a pot it was initially transferred to.
Different nurseries sell their plants at different stages of growth and use different size pots. This increases the number of pot sizes on the market.
Is pot size a good measure of value for money?
No. You don’t want a larger pot of soil, but a healthy tree with a well established root system and lots of growth. Thus, you should look at the height on arrival and the age of a tree. For larger tree sizes, looking at a tree trunk’s girth is a good measurement of value.
One particular pot size may seem very competitive in comparison to another, but this does not mean you are getting better value. Some nurseries set up complicated irrigation and fertiliser systems ensuring trees receive the best possible nutrients, while others do not go to such lengths.
Similarly, the age of a tree is not the be all and end all. A well fed tree will grow faster than a poorly fed tree. This is why you look at the height on arrival also.
Are smaller or larger pots better value for money?
The younger the tree you purchase the easier it will establish and easier it will be to train. The older the tree you purchase the greater the instant impact it will make and the less you will have to wait for fruit.
Why are 9cm pots not marketed in litres?
Interestingly, 9cm refers to the pots diameter, as opposed to height. All pots smaller than 1L are listed this way, probably because receiving a 0.43L pot sounds a bit rubbish.
Are all trees supplied in pots?
Trees can be sent from late autumn to early spring when they are dormant without any soil – these trees are known as bare root. Potted trees can be transferred anytime in the year, although are best purchased and planted in the colder months as to avoid water stress.
The smallest pot size available. Plants supplied are usually herbs and shrubs. Many hedging plants are sold this way, allowing you to grow a hedge on the cheap.
Climbing plants, both fruiting and ornamental, as well as shrubs are sold at this size.
Roses are sold at this size as their roots grow deeper than other shrubs.
The smallest pot size, you’ll likely be able to buy a tree at.
The standard size for 1-3 year old trees. Trees are transferred into this larger pot size, either from the ground or 3L pots.
As young trees are transferred to these larger pots after the bare root season ends in spring, buying in Autumn is recommended, when the tree has adapted to the pot and had more time to grow. A downside of this is that some varieties may have sold out by this point, so for lauded trees buy early!
This is the first size standards are available at. Standards have a portion of the trunk cleared of stems for ornamental value.
Trees above this size are marketed as producing an instant impact.
Trees are available in a large number of pot sizes in this range – 15, 18, 25, 30, 45, 50 and so on – with larger pots containing older, more mature trees. The greater the maturity, the greater the instant impact.
Fully grown trees are supplied at this point and at great cost, due to the cost of delivery and years in the nursery.
Approximating Plant Pot Sizes
Litres are difficult to approximate without prior knowledge. Below, you can see our infographic of the relative size of different litre plant pots.
Calculating Plant Pot Sizes
Comparing plant pot sizes is difficult as they vary in shape by manufacturer. At small sizes plant pots are flat-topped cones, while larger sizes are more structurally stable cylinders. This is why we recommend you calculate a pot’s litreage yourself.
Most plant pot sizes are measured in litres, which is a measure of volume, calculated from a shape’s cubic centimetres. A cylinder’s cubic centimetres is calculated from the equation πr2h. Thus to calculate you plant pots literage, you need to measure your pot’s height and radius with a ruler. If your plant pot isn’t an exact cylinder, but a flat-topped cone, it is best to approximate calculating a cylinder.
If your pot is a square or rectangle, calculating the cubic centimetres is easier. Simply, multiply the height by the width by the diameter.
Now you have calculated the cubic centimetres of you pot, simply divide by a thousand to arrive at litres.
Too complicated? Below you can see the measurements of various cylindrical pots that were visualised in the above infographic. In our calculations we have presumed the radius is two/thirds of the height.
In the table, you can see that a 3L pot is 44% larger than a 1L pot. Luckily, a cylindrical 3L pot will always be 44% larger than a 1L pot, regardless of the ratio of radius to height.
From the table, you can calculate how much larger a 25L pot is to a 1L pot by calculating percentage change. Simply minus the old height from the new height, then divide by the original height and then multiply by hundred. ((26.16-9)/9) x 100. Thus the percentage change is 190.67%.
We know this is correct as if we multiply 9 by 2.9067 (converting the percentage to a decimal) we arrive at 26.16.
Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!
His ideal afternoon would involve a long walk, before settling down for scones.
Jorge is a journeyman gardener with experience in growing crops.
See all of Jorge’s posts.
Potting Soil Calculator
How much soil do I need?
Let’s imagine that you want to grow herbs. You have couple small flower pots, and you don’t know how much soil do you need. Potting soil calculator can help in that problem:
- Choose the shape of the container. In our case, it’s a flower pot, so we need to calculate the volume of truncated cone.
- Enter the dimensions. For example, assume we have pots with the diameter across top equal to 4 inches, bottom base diameter of 3.2″ and height of 2.75″. Don’t forget that you can select different units, such as centimeter, feet etc.
- Set the quantity of the flower pots. We want to plant oregano, basil, and thyme, so we need to put three in the quantity field.
- The volume of soil required is equal to displayed value.
Our calculator is a flexible tool, so you can calculate everything the other way round: if you have a bag of soil and size of your containers, you can estimate how many pots can be filled.
Remember that obtained result represents the volume for the full container. Sometimes you want to fill the container to 4/5, or you already have a plant or tree with the roots and then you will need less soil. The amount of soil may also change as you squeeze it or leave it looser, so presented calculations are only a good estimator.
Shipping Container Dimensions
External Shipping Container Dimensions
20ft (6.09m) and 40ft (12.19m) are the industry standard container lengths.
For storage and other non-shipping applications other sizes are created by cutting down larger containers to the required size. The most common cut-down sizes are 8ft (2.44m), 12ft (3.66m), 16ft (4.88m), 24ft (7.32m) and 32ft (9.75m). Other bespoke sizes can also be manufactured to order. Take a look at our Shipping Container Conversions page for more conversion ideas – on how you can modify your container.
A standard container is typically 8ft 6 inches (2.59m) high.
High Cube Containers are typically 9ft 6 inches (2.90m) high.
The most common height of a container is 8ft 6ins (2.59m), though 9ft 6 inches (2.90m) high-cube containers are becoming increasingly common. In the past 8ft high (2.44m) was very common and there are some containers 9ft (2.74m) available but these are rare.
The standard width of a container is 8ft (2.44m). To accommodate some types of pallets, particularly in Europe 2.5m (8ft 2.4 inches) wide containers are available though they are less commonly available to buy on the second-hand market.
Internal Shipping Container Dimensions
The sides of a container are in nearly all cases, corrugated. The depth of the corrugation is usually 1 inch (25mm), which means that 2 inches (50mm) is lost from the external width dimension (1 inch each side). The back (blank end) is also corrugated and the doors are around 2 inches (50mm) thick meaning that approximately 3 inches (75mm) is lost from the length.
The main reduction from external to internal dimensions is with height. The floor of a standard container has an underside clearance of approximately 6 inches (150mm) and the floor has a thickness of 27mm (1.1 inches). As the roof is corrugated another 1 inch (25mm) is lost resulting in an internal dimension of around 8 inches less than external – 7ft 10 inches (2.39m), though this can vary slightly either way depending on the floor thickness and construction method used.
Through the door height is additionally reduced because of the steel top rail above the door, this is a part of the structural integrity of the container, typically it’s 4 inches (100mm) thus reducing the entrance height to 7ft 6ins (2.28m), though this can vary slightly either way.
Shipping Container Weights (Tare Weight, Gross Weight and Payload)
There are three relevant weights, the Tare Weight, the Gross Weight and the Payload. These are painted onto the outside of the container doors when it is in shipping service or before it has been repainted for another application.
- The Container Tare Weight is the weight of the container without cargo or contents.
- The Container Gross Weight is the weight of the container plus the maximum payload it can hold i.e. the maximum total weight of the container.
- The Payload (or Net Weight) is the weight of the cargo or contents that a container can hold.
|Typical Weights of Standard Shipping Containers|
|Max Gross Weight||11,300kg||30,480kg*||30,400kg|
|Payload (or Net Weight)||10,000kg||28,320kg||26,730kg|
*The most common alternative for 20fts is 24,000kg for stores manufactured to a lower specification.
Note that cut-down containers cannot hold the same weight when lifted as a standard container because the structure of the container has been altered. The container modification company should be able to supply details of capacities and advise if their design has been weight tested for lifting.
Cubic Container Capacity
|Typical Cubic Capacities of Standard Shipping Containers|
|Cubic Capacity||15.95 cubic meters||33.2 cubic meters||67.59 cubic metres|
|563.3 cubic feet||1,173 cubic feet||2,387 cubic feet|
Shipping Container Structure
Containers are designed to carry cargo. They are designed to be lifted vertically from above by cranes and transferred from ship to shore and between other forms of transport such as trains and lorries. Therefore they need to have strength in the top corners where they are engaged by the twistlocks of a container lifting crane. The corner castings in the top corners of the container are therefore points of strength.
The strength is transferred down through the corner posts to the corner castings at the bottom and then through the floor. The floor is constructed of steel cross members approximately 6 inches (150mm) deep, which are approximately 20 inches (508mm) apart (laterally across the container) and give transverse strength and support the floor. The cross members are welded at each end to longitudinal beams which run the length of the container between the corner castings. This all means that the strength of a container lies within the corner posts and the floor. Structural alterations or damage to these components will weaken the container.
The information contained here is for guidance only. ContainerContainer do not accept any responsibility for any loss or damages resulting from use or interpretation of this information.
Have you ever wondered about those pot size descriptions for shrubs, perennials, or trees? It can be very confusing when you think you are getting a bargain plant, only to find it shipped in a tiny little pot, and looks like something resembling a small twig. But, when you break it down, does larger size mean a better plant? It can…. but just what is the difference?
The plant pots used generally in local and online retail nurseries use a standard group of containers, called “trade pots” to grow and sell their products. Plants can be sold in quart, gallon or other sizes. But why, when you read the plant will be shipped in a 1 gallon pot, it doesn’t really look like it will hold 1 gallon of soil?
The American Standard for Nursery Stock offers a bit of clarification in this area. It was created to provide buyers and sellers of plant stock with a standard terminology to allow a clearer explanation of pot sizes, as well as other aspects, such as width and height ratios for plants to grow well in different sized containers. This standard was not intended to be a true plant quality indicator, but it can help to provide for minimum expectations for the best growth.
So here is a basic breakdown as to what those size listings actually mean to help clear up any questions:
At Lots of Plants, our shrubs are most often sold in 3 gallon containers. We do offer some shrubs in 1 quart and 1 gallon sizes. We strive to offer higher quality plants and like the concept of selling a larger sized, more established plant that is ready to go, and holds up better to environmental changes. One of our personal favorites is the Green Velvet Boxwood. This hardy plant is a great foundation shrub or mass hedge, with its deep green color that creates structure for your home year round. The Crimson Fire Loropetalum is another winner as a great companion plant for the boxwood with its burgundy-purple foliage and fringed hot pink flowers. Both of these shrubs are low maintenance, and great focal points for the busy homeowner. Usually a 1 gallon container, or #1, is most often seen when you buy perennials and smaller shrubs. Pots sized as 3, 5, and 10 gallon pots are often for shrubs, and 15 gallon pots for trees.
Browse our plants to check out more of our versatile, established shrubs and ready to create the yard you are dreaming about. And if you have any questions or problems, we are happy to help, just contact us by calling 336.999.8196 or email us at [email protected]
Understanding Nursery Containers – Common Pot Sizes Used In Nurseries
Inevitably you’ve come across nursery pot sizes as you have browsed through mail-order catalogs. You may have even wondered what it all means – what is #1 pot size, #2, #3 and so on? Keep reading for information on the common pot sizes used in nurseries so you can take some of the guesswork and confusion out of your selections.
About Nursery Plants Pots
Nursery containers come in a number of sizes. Oftentimes, the particular plant and its current size determine the pot sizes used in nurseries. For instance, most shrubs and tree are sold in 1-gallon (4 L) pots – otherwise known as a #1 pot size.
What is #1 Pot Size?
The gallon nursery containers, or #1 pots, are the most common nursery pot sizes used in the industry. While they normally only hold 3 quarts (3 L) of soil (using liquid measure), they are still considered to be 1-gallon pots. A variety of flowers, shrubs and trees can be found in this pot size.
As the plants grow or mature, nursery growers may step up the plant to another larger size pot. For instance, a #1 shrub may be stepped up to a #3 pot.
Variations in plant pot sizes can be quite different among individual nursery growers. While one nursery may ship a large, lush plant in a #1 pot, another might only send a bare, twiggy-looking plant in the same size. For this reason, you should research beforehand to make sure of what you are getting.
Grade of Nursery Plant Pots
In addition to the various pot sizes, some nursery growers include grading information. As with the variations among sizes, these too may vary among different growers. These are usually dependent on how a particular plant has been grown (its conditions). That said, the most common grades associated with plant pots are:
- P – Premium grade – plants are normally healthy, big and more expensive
- G – Regular grade – plants are of moderate quality, fairly healthy, average cost
- L – Landscape grade – plants are of less quality, smaller and least expensive choices
Examples of these might be #1P, meaning a #1 pot size of premium quality. A lesser grade would be #1L.
Understanding Nursery Stock Sizes
It’s time to build your plant lists…. And there’s one thing to remember. Size matters! But understanding and deciphering standard nursery stock sizes can be like trying to find your way out of an Iowa cornfield. You’re bound to get lost a few times. Everyone calls out nursery stock sizes differently. Gallons, flat size, tree height, or caliper have all appeared in our plant lists. But depending on your familiarity with the nursery industry, you may not know that there is a continuously updated national standard on how to spec nursery stock sizes!
When writing this blog, I set out to include a nice handy, dandy all-purpose cheat sheet for our landscape professionals but it turns out that is easier said than done! Instead, this article provides a brief overview of the standard and can get you started on the right path to learning more for the next time you specify plants. We cannot promise that your suppliers will be following this standard to the number and letter, but if you stay familiar with the standards you will be much more likely to specify the nursery stock sizes that are available.
Specifying the Right Sizes Takes Knowledge
Called the American Standard for Nursery Stock, this national standard is published and maintained by AmericanHort, which is a somewhat recently formed consolidation of the American Nursery & Landscape Association and OFA—The Association of Horticultural Professionals.
According to AmericanHort, “The purpose of the American Standard for Nursery Stock … is to provide buyers and sellers of nursery stock with a common terminology, a ‘single language,’ in order to facilitate commercial transactions involving nursery stock. For instance, the Standard establishes common techniques for (a) measuring plants, (b) specifying and stating the size of plants, (c) determining the proper relationship between height and caliper, or height and width, and (d) determining whether a root ball or container is large enough for a particular size plant.”
The organization has been publishing this nursery standard since 1923, and it was adopted as a national standard in 1949 (ANSI Z60.1-2014). The most recent revision to the standard was published in 2014, and is available free from AmericanHort HERE. Use of this standard when growing and specifying plants is voluntary, but it is widely accepted and often referenced in standard specification sections. Using the standard has many benefits for designers and contractors, not the least of which is simplifying the procurement and acceptance processes by relying on clear pre-defined standards for quality and size of nursery stock.
The complete standard may be a daunting 109 pages but it is a surprisingly easy read, and provides in-depth, but digestible information. Below are a few key points from the American Standard for Nursery Stock you may find helpful (along with a cheat sheet to get you to the appropriate tables in the larger document). However, we would HIGHLY recommend reading through the whole standard and having a copy handy. It truly provides an amazing wealth of info (there’s a great section on identifying unacceptable co-dominant leaders – a problem I’ve had first hand issues with!). This resource also provides all the information necessary when accepting or rejecting plant material that shows up at your site!
Read on below for a summary of what you will find in the standard. Or, if you’re looking for other ways to make specifying plants easier check out The Plantium!
General Standards for Nursery Stock Sizes:
- Specifications must include plant size by caliper, height or width appropriate to the plant type.
- Certain plants may be specified by container size (see below). ALL others should be specified with caliper, height or width.
- Typically, plant size specifications should include only the minimum allowable plant size in that interval. In other words, if you specify a 2.5 in. caliper Type 1 shade tree you may get a tree anywhere up to a 3 in caliper because it references the 2.5 to 3 inch range for that type of tree. As long as you specify the minimum, you know you will not get a SMALLER tree.
- Caliper is always measured six inches above ground or soil level for trees less than 4.5” caliper, and 12 inches above the ground for 4.5” or larger.
General Standards for Containers:
- These are generally the only plants to specify by container size
- Herbaceous perennials
- Non-winter-hardy shrubs
- Ornamental grasses
- Containers marketed and sold with a # designation must have volumes within the ranges shown in the ANSI standard in order to comply
- Container classes #1 through #100 include the volume of a container that, if such a container were manufactured, would hold the equivalent number of gallons as the container class number. #1 = one gallon; #5 = five gallon and so on.
- Nursery stock specifications that reference only an imperial volume measurement, such as “quarts” or “gallons,” are not in accordance with the Standard. I can tell you that our plant lists have gotten that WRONG for years!!
- The SP designation refers to ‘small plant’ containers. #SP4, for example, is a 4 inch container, or “quart” container. This designation goes from #SP1 – #SP5 and should reference square or round.
- Container grown nursery stock shall have a well-established root system reaching the sides of the container to maintain a firm ball, but shall not have excessive root growth encircling the inside of the container (the same holds true for roots in ball and burlap!).
Container Growth Gone Wrong – Root Bound Tree
When Done Right – A Thing of Beauty
Shade and Flowering Trees:
- There are FOUR types of shade and flowering trees identified in the standard with the following associated specifications tables
- Type 1 – Page 15-16
- Type 2 – Page 17
- Type 3 – Page 19
- Type 4 – Page 21
- Multi-stem and Shrub Form Trees – Page 24
- Multi-stem tree specifications should include a minimum number of stems. If none is specified, 3 will be assumed.
- There are THREE types of deciduous shrubs identified in the standard with associated specifications
- Type 0 – Page 28
- Type 1 – Page 28
- Type 2 – Page 29
- Type 3 – Page 30
- Plants may not meet plant size specification or minimum number of canes at time of shipment at certain times of the year, but would be expected to reach the plant size specification and minimum number of canes during the first growing season after shipment.
- There are SIX types of Coniferous Evergreens identified in the standard with associated specifications
- Type 1 – Page 32
- Type 2 – Page 33
- Type 3 – Page 34
- Type 4 – Page 36
- Type 5 – Page 38
- Type 6 – Page 40
- Coniferous evergreens will also be described by their shearing:
- Natural: (showing the form natural for the species)
- Semi Sheared (sheared when plant is young to maintain symmetrical shape)
- Sheared (pruned regularly to retain a symmetrical shape)
- Altered Form (Can you say POODLED!!)
- There are SIX types of Coniferous Evergreens identified in the standard with associated specifications
- Type 1 – Page 42
- Type 2 – Page 44
- Type 3 – Page 46
- Type 4 – Page 48
- Type 5 – Page 50
- Type 6 – Page 52
Additional information in the standard provides specs for young plants, roses, palms (and other bare root stock), fruit trees, bulbs, corms/ tubers, and understock/seedling trees and shrubs.
Now, armed with this great information, you can confidently go forth and specify!
Also, check out these other great articles regarding considerations on transplant size:
Container and growing pots come in a variety of sizes. In the United States nursery and garden centers sell pots by the size in inches and gallons. In the United Kingdom, Europe, and most of the rest of the world containers are sold by the size in centimeters and liters.
There are few standards when it comes to container sizes and volumes. To determine the size of a pot measure across the top from one side to the other to determine how many inches or centimeters it is. However, because some pots are long and others are squat and because the sides of some pots are straight and others are tapered, the volume can vary.
When it comes to filling a pot with soil estimating how much soil you need is an approximation. Often the volume of a container is measured in liquid quarts or liters, but, of course, when you purchase soil you are purchasing dry (potting soil is not liquid). A dry quart is equal to about 1⅛ liquid quarts. When deciding how much soil to purchase it’s best to factor soil compression that commonly results from moistening and pressing the soil into the pot. Soil compression can add another 15 to 20 percent dry soil to the container. Also take into consideration that when you transplant a plant from one container to another, you will be moving some soil around the roots of the plant.
Take notes on the pots you have and the soil they require. In short order, you will have a realistic estimate of how much soil you will need to purchase when potting plants.
Standard Clay Pots and Plastic Nursery Pots
This chart will help you translate container sizes for standard clay pots and black nursery pots and give you an approximation of how much soil each will require (again these are dry soil measures):
4 inch pot (10 cm) = 1 pint (0.5L)
5-6 inch pot (13-15 cm) = 1 quart (1L) = 0.03 cu. ft.
7-8 inch pot (18-20 cm) = 1 gallon (4L) = 0.15 cu. ft.
8.5 inch pot (22 cm) = 2 gallon (7.5L) = 0.3 cu. ft.
10 inch pot (25 cm) = 3 gallon (11L) = 0.46 cu. ft.
12 inch pot (30 cm) = 5 gallon (19L) = 0.77 cu. ft.
14 inch pot (36 cm) = 7 gallon (26L) = 1 cu. ft.
16 inch pot (41 cm) = 10 gallon (38L) = 1.5 cu. ft.
18 inch pot (46 cm) = 15 gallon (57L) = 2.3 cu. ft.
24 inch pot (61 cm) = 25 gallon (95L) = 3.8 cu. ft.
30 inch pot (76 cm) = 30 gallon (114L) = 4.6 cu. ft.
10 inch (25 cm) = 5.5 dry quarts (6L) = 0.21 cu. ft.
12 inch (30 cm) = 7.9 dry quarts (8.4L) = 0.3 cu. ft.
14 inch (36 cm) = 13.9 dry quarts (15.3L) = 0.5 cu. ft.
8 inch (20 cm) = 1.9 dry quarts (2L) = 0.07 cu. ft.
10 inch (25 cm) = 3.7 dry quarts (4L) = 0.14 cu. ft.
12 inch (30 cm) = 5.5 dry quarts (6L) = 0.21 cu. ft.
14 inch (36 cm) = 8.4 dry quarts (9.2L) = 0.29 cu. ft.
16 inch (41 cm) = 12.0 dry quarts (13.2L) = 0.46 cu. ft.
18 inch (46 cm) = 18.8 dry quarts (20.7L) = 0.73 cu. ft.
21¾ inch (55 cm) = 31.2 dry quarts (34.3L) = 1.21 cu. ft.
12 inch (30 cm) = 3.8 dry quarts (4.1L) =0.14 cu. ft.
16 inch (41 cm) = 7.3 dry quarts (8L) = 0.28 cu. ft.
20 inch (51 cm) = 9.4 dry quarts (10.3L) = 0.36 cu. ft.
12 inch (30 cm) = 11.2 dry quarts (12.3L) = 0.48 cu. ft.
15 inch (38 cm) = 23.0 dry quarts (25.3L) = 0.89 cu. ft.
24 inch (61 cm) = 11.7 dry quarts (12.8L) = 0.45 cu. ft.
30 inch (76 cm) = 15.6 dry quarts (17.1L) = 0.6 cu. ft.
36 inch (91 cm) = 19.7 dry quarts (21.6L) = 0.76 cu. ft.
5 gallon = 14 dry quarts (15.4L) = 0.54 cu. ft.