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Jessica Walliser

In container gardening, size does matter

Jessica Walliser
| Thursday, May 10, 2018, 8:55 p.m.
The larger a container is, the higher the volume of soil it can hold, and the higher soil volume you have, the less often you have to water.
Jessica Walliser
The larger a container is, the higher the volume of soil it can hold, and the higher soil volume you have, the less often you have to water.

Question: I read some of your previous articles that talked about gardening in containers. I'm getting older and plan to grow all my flowers and vegetables in pots this year. When I've tried growing in pots in the past, I've never had much luck. I think maybe I was using pots that were too small. Do you have a size recommendation for containers? How big should they be?

Answer: There are many reasons to garden in containers, instead of in the ground. Container gardening is lower maintenance than in-ground gardening (no weeding or mulching required), containers can be moved to maximize sunlight, and you don't need a lot of space to grow a hearty yield of veggies and herbs when growing in pots.

But, choosing the right-sized container is absolutely essential. I hear from a lot of gardeners who are disappointed in the performance of their container garden, and in these cases, I often discover that the culprit is either puny pots or inadequate irrigation. These two issues really go hand-in-hand.

The larger a container is, the higher the volume of soil it can hold, and the higher soil volume you have, the less often you have to water. So, this means you should always opt for pots that hold an ample amount of soil and match up with the space needs of whatever crop you're planning to grow. When you do this, you'll find irrigating is easier and the pots don't dry out as quickly. Still, no matter what pot size you pick, regular irrigation is essential to a healthy container garden.

Here's the guide I use to determine what size pot to use for each plant I'm growing.

Keep in mind that the container sizes found in this list hold the minimum soil volume needed by that particular plant.

Minimum soil volume needed for specific plants:

• 20-30 gallons minimum for each shrub or other large plant, including figs, blueberries, hydrangeas, tropical flowering plants and many others.

• 10-15 gallons minimum for each extra-large vegetable, such as full-sized tomatoes, winter squash, pumpkins, and melons.

• 8-10 gallons minimum for each large fruit or vegetable plant, including peppers, eggplants, tomatillos, cucumbers, summer squash/zucchini, and bush-type winter squash varieties.

• 5-8 gallons minimum for each medium-sized vegetable or flowering plant, including cabbage, broccoli, cauliflower, Brussels sprouts, bush-type cucumbers, and okra, This is also the suggested minimum soil volume for each flowering or foliage perennial or ornamental grass included in a container.

• 1-2 gallons minimum for each small-statured vegetable or flowering plant, including many flowering or foliage annuals, kohlrabi, lettuce, kale, chard, collards, spinach, and other greens. Individual herb plants fit into this category as well.

Plants that are usually grown in a group, such as strawberries, corn, bush beans, peas and roots and tubers such as potatoes, carrots, beets, radish, onions and turnips can be planted in almost any sized container, as long as the seeds or plants are spaced at the appropriate distance for optimum growth (as noted on the plant tag or seed packet) and the pot is deep enough for the roots to have ample room to grow. The smaller the pot is, though, the fewer seeds or plants it can house.

If you plan to combine different plants together into the same pot, then you'll need to add these measurements together to ensure there's enough room for all of the plants in the container to produce an ample root system. For example, if you want to combine a tomato plant with a pepper plant and a few herbs, you'll need a container that holds at least 20-28 gallons of potting mix.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is Send your gardening or landscaping questions to or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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