Whenever I mention that I grow many kinds of vegetables in containers, someone almost always asks me what size pots I use for specific veggies. At first it was hard to give a helpful answer since pot size is usually measured in diameter inches at the rim, but the depth of the container matters just as much for vegetables. And that can vary. Not all 18-inch pots are the same depth.
So, a few years ago whenever I tried a new vegetable, I measured the amount of potting mix that went into each container. For my “measuring cup,” I used a standard gallon-size pot that you buy shrubs and some large perennials in. Every gardener has at least a few of those black plastic pots sitting around.
Then I watched to see how the vegetables performed in the amount of potting mix they were given. I figured out that some needed at least 5 gallons of soil (five of the black pots full to the rim with potting soil) and some could get by with 3 gallons (provided I wanted to grow only one plant in that size pot).
In hopes that others will find my experimenting useful, here’s my list. Note that these are minimum sizes for the number of plants given. If you want more plants in a single container, it obviously will have to be bigger.
Leaf lettuce, peas, and onions aren't on the list because the method is slightly different for them, since they're all started from seeds (or, for onions, sets). While you might grow one tomato plant, you’d never grow one onion. So with this trio, start with at least a 5-gallon container (10 gallons for peas) and space the seeds 8 inches apart for lettuce, 3 inches for onions, and 2 inches for peas. That determines how many plants you grow.
For general information on growing each crop, click on the name of it. You’ll need to provide support for the veggies marked with an asterisk.
Whenever possible, choose space-saving vegetables for containers. You may be surprised at how well they yield.
Beets, 7 plants, 3 gallons soil
1 plant, 4-gallon pot
, 1 plant, 3-gallon pot
1 plant, 5-gallon pot
Cucumber*, 1 plant, 3-gallon pot
Eggplant, 1 plant, 5-gallon pot
Pepper, bell, 1 plant, 3-gallon pot
, 1 plant, 2-gallon pot
Radish, 12 seeds, 1-gallon pot
, 3 plants, 2-gallon pot
Squash, 1 plant, 5-gallon pot
Tomato*, 1 plant, 5-gallon pot