Decoding Nursery Pot Sizes: A Guide to Common Container Classes

If you've ever browsed a mail-order plant catalog, you've likely encountered cryptic designations like #1, #2, or #5 pot sizes. These numbers can be confusing, but they're actually a standardized system used by nurseries to indicate container volume and, by extension, the approximate size of the plant inside. Understanding this system takes the guesswork out of selecting the right plant for your garden.

How Nursery Container Sizing Works

Nursery pots come in a range of sizes, typically dictated by the plant's species and current growth stage. For example, most shrubs and young trees are sold in 1-gallon containers — referred to as #1 pots. The "#" symbol denotes the container's class number. Smaller pots, such as 4-inch containers, may carry an "SP" prefix (e.g., SP4) to indicate a smaller plant size. As a general rule, the higher the number, the larger the pot and the more mature the plant.

Standard sizes progress from #1, #2, #3, and #5 up to #7, #10, #15, #20, and beyond. While these sizes correlate loosely with gallon volumes, they are not exact liquid measurements.

What Is a #1 Pot?

The #1 container (often called a "gallon pot") is the industry standard. Despite the name, these pots typically hold about 3 quarts of soil, not a full gallon. They're used for a wide variety of perennials, shrubs, and young trees. As plants grow, nurseries "step them up" into larger containers — a #1 shrub might move to a #3 pot for further development.

Keep in mind that plant size within the same pot class can vary significantly between growers. One nursery's #1 plant may be full and lush, while another's might be sparse. Researching the supplier beforehand helps ensure you know what you're getting.

Plant Grades: Quality Indicators

Beyond size, some growers assign quality grades to their plants, often noted as a letter after the pot size (e.g., #1P, #1L). These grades reflect growing conditions and overall plant health:

• P – Premium grade: Vigorous, well-branched, larger specimens; higher cost.
• G – Regular (Garden) grade: Average quality and size; moderately priced.
• L – Landscape grade: Smaller, less developed; most economical.

These designations aren't universally regulated, so they can differ between nurseries. When in doubt, ask the seller for clarification on what their grades mean.