This is one article in a series of four on container garden design. You can access the other three articles here:

On the other hand, plants that are more compact and have an upright nature may take more than the recommended number to make the planter seem full. Pansies are an example of a rather compact, upright, slower-growing plant. Pansies are fantastic for cool season color. However, they tend to be relatively small plants and are primarily grown when the weather is cool which means they grow more slowly. When I plant pansies in pots, I tend to use a lot more than the recommended number of plants I gave above. The photo below was taken at the end of October and the container was planted at the end of September. This is a 12-inch container and it has eight plants in it. The planter is full without being overly crowded. It had rained for three days prior to taking this photo so the plants are looking a bit forlorn. 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.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. 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? Often spacing is included on plant tags. This spacing refers to the preferred spacing for in-ground plantings. However, you can use the spacing information as one way of estimating final size and vigor. Plants that have a smaller spacing recommendation are generally going to be smaller and less vigorous. Those with a larger spacing recommendation are generally going to be larger and more vigorous plants. You can use that information to help determine the number of plants to include in your planters. As you are planting, try and spread the plants somewhat evenly throughout the planting area of the container while leaving some space between the edge of the container and the root ball of the plants. If you do that, your planters will look great. 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, Ilearned that… nobody agrees, even slightly, right down to whether it should be listed by pot volumes or pot diameters.

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: 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. 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 trees are sold in 1-gallon (4 L) pots – otherwise known as a #1 pot size. If you are planting a mono-crop (all one plant), you can simply put one plant in each spot. If you are planting a combination planter (several different kinds of plants), you need to pay attention to color, texture, habit and height.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). 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? 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.