What size pot do herbs and vegetables need?
Most herbs grow well in a 2- to 5-gallon pot, and leaf lettuce needs as little as half a gallon. Tomatoes and peppers need 5 gallons, or 2 for a cherry tomato. Those are University of Maryland Extension's minimums (UMD Extension).
University of Maryland Extension says to match the container to the plant, counting the roots as well as the top growth. If you restrict the roots too much, it says, plants won't grow well (UMD Extension).
Minimum pot sizes
From University of Maryland Extension's container guide. Bigger is fine. These are the smallest sizes it lists.
| Plant | Smallest pot |
|---|---|
| Leaf lettuce | ½ gallon |
| Beets | ½ gallon |
| Swiss chard | 2 gallons |
| Bush beans | 2 gallons |
| Cherry tomatoes | 2 gallons |
| Basil, cilantro, thyme, mint, oregano | 2 to 5 gallons |
| Standard tomatoes | 5 gallons |
| Peppers and eggplant | 5 gallons |
| Rosemary, sage, parsley, dill, bay | 5 gallons or more |
UMD adds that depth and shape matter too. A 5-gallon pot that's wider than it is tall is steadier in a breeze than a tall, narrow one of the same size.
Drainage holes
UMD says every container needs holes or slits so extra water can drain. Rocks or gravel at the bottom don't help. They can raise the water level in the pot and leave the mix waterlogged. Illinois Extension says the same, and warns against saucers that can't be emptied (Illinois Extension).
Self-watering planters work differently. The mix sits above a water reservoir, roots grow down into it, and an overflow hole on the side lets extra water out (UMD).
What to fill it with
Use potting mix, not garden soil. UMD says soil is too dense for a container, at about 75 pounds per cubic foot, and it can drown roots. Potting mix weighs about 10 pounds per cubic foot and drains well. As a guide, UMD says a 2-cubic-foot bag fills three 5-gallon buckets or grow bags.
How heavy it gets
UMD says a 20-inch pot of moist mix and plants can weigh 100 pounds. A wheeled plant caddy makes a heavy pot easier to move. On a balcony, check your lease or building rules and your balcony's load limit before you fill a big planter. If you garden above a neighbor's balcony, UMD suggests a saucer, emptied often, or a self-watering pot with no bottom holes.