Growing vegetables in containers can bring you both joy and bounty. There's a simple pleasure in biting into a tomato still warm from the sun—picked and eaten on the spot. You can grow just about any vegetable in a container, a practice that can save you lots of money buying produce at the grocery store. However, vegetable container gardening can be a frustrating endeavor if your plants don't thrive and produce. It helps to know that for larger plants to flourish, you may need a deeper container to hold about 12 inches of soil. For example, a 5-gallon container would work for tomatoes and squash but a smaller container is better for plants like lettuce, which has shallow roots. Following are more tips for growing vegetables in containers to help you and your plants get off to a good start.
Providing the Right Light and Temperature
Most fruiting vegetables, like tomatoes and peppers, need full sun, meaning at least six hours of direct sunlight each day. But some gardeners might overestimate how much sun an area really gets. For your veggies to thrive, you'll need an accurate assessment. Check the location every 30 minutes throughout the day to confirm how long the sun directly hits the spot where you want to put your vegetable container garden. You can also use a sun calculator to get an accurate assessment.
If you live in a hot climate, you might need to shade your plants during the heat of the afternoon, so they don't overheat. Also, it's best not to use metal or dark-colored containers because they can become very hot and cook your plant's roots.
On the flip side, many vegetables don’t like cold soil. So if you live in a cool climate, avoid putting your containers outside full time until you know the temperature will be reliably warm. For many plants, the soil needs to be at least 60 degrees Fahrenheit. You can use a thermometer to find out the temperature of your soil. In addition, always make sure to harden off your seedlings (gradually acclimate them to the outdoor conditions) before you put them outside permanently.
Watering Your Container Garden
Many vegetable plants, such as tomatoes, need lots of water. However, you don't want to drown your plants. The goal is to keep the soil evenly moist but not soaking wet.
To figure out whether your plants need water, stick your finger down into the soil about an inch. If the soil feels dry, add water; if you're not sure, wait and check later in the day. At the height of summer, you'll probably need to water at least once or sometimes twice a day. This is often the most high-maintenance and critical aspect of vegetable container gardening.
Using Quality Potting Soil
High-quality potting soil is important for vegetables. Don't use soil from your garden, because it will compact in the containers and won't drain water properly. Also, one of the reasons to garden in containers is largely to avoid dealing with weeds and soil-borne diseases. But if you use garden soil, you might be importing problems into your containers.
Feeding Your Plants
Plants need nutrition to thrive, and their food is fertilizer. If your soil doesn’t have fertilizer already mixed in, add some several times throughout the growing season, according to the directions on the label. Many gardeners mix organic, granular fertilizer into the containers before planting. Then, every couple of weeks, add diluted liquid fish emulsion or liquid seaweed to give the plants the nutrition they need. Another way to add nutrients is to make or buy compost, which helps feed the plants.
Creating Optimal Drainage
Drainage is key to keep plants from drowning. Your container should let excess water out of the bottom, so your plants won't sit in overly soggy soil and succumb to root rot. There should be one large hole or several smaller holes located at the base of your container.
You can usually drill holes in the pot if the drainage is insufficient, and you can cover a large hole before adding soil with a coffee filter or plastic screening to keep the dirt from coming out the bottom. If your container sits on a hard surface, the hole might plug up. Elevating your container with pot feet or a pot cart will help your plants drain with ease.
Selecting the Perfect Container
Choosing a container can be daunting. You can use almost anything for a garden planter as long as it's big enough, has good drainage, and is made of food-safe material. But keep in mind that the larger your container is, the easier it will be to maintain. The more soil a container can hold, the more moisture it will retain. In general, don’t bother with containers that are smaller than 12 inches across. Bigger really is better when it comes to growing vegetables in containers.
Wooden containers look lovely when growing vegetables, and you can typically find optimal-size containers that aren’t too expensive. Or you can make your own wooden planter box. Just remember that after a few seasons, wooden containers may begin to rot.
Growing vegetables in self-watering containers works well, too. They are large, easy to use, and incredibly durable. And they make watering plants a cinch because all you have to do is keep the water reservoir full.
You also can use food-grade plastic or glazed ceramic containers. You can even use terra cotta pots, but it's harder to keep your plants moist in them, because the clay allows the water to evaporate out of the soil more easily. To help solve this problem, you can line a terra cotta pot with plastic, use a plastic pot as a liner, or seal the pot with a stone sealing product. Remember, though, that because ceramic and terra cotta pots draw moisture into their materials, they can shatter if left outside in freezing weather. Make sure to store them inside during the winter.
For an inexpensive container, use a 5-gallon plastic bucket from the hardware store and drill holes in the bottom. Another alternative is to make an unusual container from something you have around your house, such as an old laundry basket or toy bin. As long as it’s big enough and has good drainage, you can really use anything.
Choosing Seeds or Seedlings
You can start your veggies from seed or buy seedlings. There are some significant advantages and disadvantages to each. Planting your own seeds is much less expensive than buying seedlings. Plus, you can organically grow hard-to-find varieties.
However, starting seeds isn't for everyone. They need 12 to 16 hours of light per day and good air circulation to grow up strong. Plus, you absolutely cannot let the seeds dry out, or they're toast. Conversely, if you give them too much water, they’ll keel over dead. To avoid this, you can make a self-watering seed starter.
Vegetables for Container Gardens
When choosing vegetables to plant in containers, look for bush or small varieties (often referred to as dwarf or compact), and ensure that your climate has enough growing days for the required time to mature.
Plants that typically grow well in containers include:
- Peas: Put tall supports in the container when planting seedlings. Water frequently, and keep them fertilized.
- Potatoes: Some potatoes need a 120-day growing season, so look for varieties that mature early.
- Tomatoes: Like peas, tomatoes need a support system. Use a rod or tomato cage to keep your plants upright.
- Carrots: Use a container that's double the depth your variety will grow.
- Radishes: Containers don't have to be that large for this spring and fall vegetable.
- Eggplant: When planning which variety to buy, know that many eggplants are fairly sensitive to cool temperatures (lower than 50 degrees Fahrenheit).
- Summer or zucchini squash and cucumbers: Choose bush varieties rather than the sprawling vine varieties. One plant can fill a 24-inch pot quickly, so don't crowd your seeds or seedlings. A trellis in the pot will supply support for the fruit and allow air to flow around the plant.
- Leafy greens: Spinach and leaf lettuce are among the many greens that you can snip to eat one day and then snip again a few days later. Grow the cool-season crops in spring or fall. They also tolerate partial shade.
- Peppers: Try traditional bell peppers, or spice it up with hot peppers that are perfect for homemade salsa.
Plants that don't usually work well in containers include:
- Large melons
- Large pumpkins or squash
Plants Grown in Containers. North Carolina State University Extension.
Drowning and Edema. University of Illinois Extension.
Soil Borne Diseases. UC Davis Global Soil Health Portal.
Starting Plants From Seed. University of New Hampshire.