How often have you strolled through a farmer’s market or eyed a friend’s fresh produce and wished you had your own garden? Perhaps you lack space. Perhaps you live in an apartment, or have no accessible dirt on your property. Or, if you’re like me, chickens take up much of the space that would otherwise be dedicated to gardens. Growing vegetables in pots and containers make it possible to garden in apartments, on rooftops, driveways, and on top of infertile soil. Reaping a bounty is easy if you obey a few rules of growing vegetables in pots.
This is the mistake I see most often in container gardening. People choose a 6-inch pot and hope to grow carrots, or think they can leave their tomatoes in the same container used for marigolds. Root space is critical to healthy plants. Those tomatoes may flourish in a 12-inch container until the plant becomes so rootbound and thirsty it can’t take it anymore. Then it will pale and droop and eventually die.
What Grows Up Must Grow Down
If you want to know exactly how much root space your plant will need, look at the plant itself. The root system of a healthy plant mirrors the top. If a carrot reaches 18 inches above the soil, the long taproot will go down about 18 inches. Tomato roots reach as far out to the sides as their branches. You can grow these plants in pots smaller than their potential, but this will hinder your produce as the roots twine around each other until they become a solid mat. When the tail-like end of the carrot touches the bottom of the pot, it simply will not grow down further. Thus, the thick part of the root will be much shorter than you expect.
You don’t need to spend $10 to $40 per container. Metal washtubs, barrels, wooden boxes, plastic buckets … We’ve built containers out of old bed frames and pallets, and even out of 55-gallon plastic drums. Three things are important:
- Drainage. Drill small holes in the container, if they aren’t already present. You may also need to set the container on an elevated surface, such as a block of wood, if the ground doesn’t allow the water to go anywhere once it’s left the container.
- Size. If you think your container is big enough for the plant you want … go bigger.
- Color and material. In some climates, this doesn’t matter. But if you live within the relentless sun of the desert, planting in a metal washtub might sear your roots. Also, black containers can heat up in the sun. This is easily solved by spray painting the container a light color or covering it with an attractive surface like coiled rope.
Potting soil is critical for container gardening. Clay hardens up and pulls away from the sides. Sand drains fast and often doesn’t hold enough loam to feed the plant. Commercial potting soil is well worth the money once you get strong yields. You can use the soil year after year, as long as you supplement with manure and compost to replace lost nutrients. Also, price matters. The most expensive potting soils do indeed produce the best plants.
Every plant needs at least six hours of direct sunlight to flourish. Some crops, such as lettuce and spinach, can get by on the very minimum. Most others want at least 12 hours of sun. You simply cannot grow a successful garden in a corner of your patio that gets two hours of sun a day. Before you place your pots, pay attention to the sun and the shadows around your property. You may need to place your containers in a less convenient area.
Though I just mentioned that you might need to trek across your yard to reach your containers, try to put them in the most convenient place possible. The best gardens are closest to the house. If you’re short on time and can place the containers right by the spigot and hose, you’re less likely to neglect your plants.
Containers can parch during the summer, especially if you live in an arid climate. Growing roots spread through the soil, sipping away all available moisture. Pay attention to the soil. If you insert your finger into the dirt and cannot feel dampness within one inch, your plants need water. Mulching helps alleviate this. You can spread dry grass over the top of the soil, or a thin layer of light-colored plastic with ventilation holes.
Hardware stores sell tomatoes in March. They’re not psychic and don’t think the weather won’t turn cold again. Customers trust the stores, plant their tomatoes outside, weep as plants die in the bitter cold, and return to buy more. I once sat beside a woman who bemoaned that she replanted her tomatoes four times due to the weather. We were still three weeks away from the average last frost of the season.
Containers can be carried inside during cold nights. You can position ultraviolet lights above them if your area receives a late-spring snowstorm. But pay attention to the seasons. Roots are more susceptible to cold while in containers than they are in the ground. The heat of summer can be exacerbated if you set your pots on a blacktop driveway. No matter where you plant them, lettuce will bolt in the heat and tomatoes will die in a frost.
Though some plants are not recommended for container gardening, you can still do it.
Growing Garlic: Planted in the fall, garlic depends on a hibernation period to reset the bulb for early spring shoots. Containers do not provide enough protection. While solid ground can protect the bulbs, containers will freeze and destroy them.
Growing Pumpkins and Squash Varieties: The root system of pumpkins can survive in pots, but the long, trailing habit makes gardening in small spaces difficult. If you do put your pumpkins in pots, be sure you have at least 20 feet on either side that can support the vining plants.
Growing Sweet Corn: Because corn is wind-pollinated, it must be planted in at least a 4’x4’ block to receive a good harvest. This makes container gardening difficult because of the amount of space necessary. Again, it can be done if you have enough dedicated containers. Corn does thrive best in solid ground and will give you the best harvests if you can sow large swaths of land.
The following sizes are classified by depth, not width for growing vegetables in pots. These plants can be grown in smaller containers or pots, but the plant will suffer when it becomes root-bound. To estimate recommended space between multiple plants in the same pot, take the depth of the pot and divide it in half. For instance, when growing lettuce in containers, plant lettuce at least 3 inches apart.
- Asian greens
- Bush beans
- Onions and leeks
- One pepper plant
- One small eggplant
- “Patio” tomatoes
- 5 or 6 pole habit beans, with support
- 2 pepper plants
- Determinate tomatoes
- 2 small-fruit eggplant or one large-fruit eggplant
- 1 melon or squash plant, with support
- Indeterminate tomatoes
- 3-4 peppers
- 3-4 small-fruit eggplant or 2 large-fruit eggplant
- 2 melon or squash plants, with support
These are walled boxes or cylinders, without bottoms, set directly atop decent soil. Roots hit the ground and keep going. Almost anything can flourish, as long as the width of the planter is adequate for the roots.
Do you container garden with success? We’d love to see pictures of growing vegetables in pots wherever you call home!
Originally published in 2014 and regularly vetted for accuracy.