A Question of the Week

Growing tomatoes in containers is a great option for anyone who doesn’t have a place for an in-ground garden, is concerned about what is in their soil or simply enjoys the look and convenience of having tomatoes on the porch or patio. Though almost any vegetable can technically be grown in a container, tomatoes are one of the easiest and most popular. Given the right growing conditions, a single potted tomato can produce a considerable amount of fruit. All it takes is growing them in a place where they will receive at least 6-8 hours of direct sunlight a day and providing sufficient water. Producing tomatoes at home on a small scale can be much more expensive than purchasing them at the store. By the time you buy a container, potting mix, fertilizer and plants, you may be looking at spending at least $30 for only ten slicing tomatoes.  However, as home-grown, vine-ripened tomatoes far exceed the quality and flavor of store bought, you may find that growing them in containers is still worth the effort.

Choosing the Right Plants

Tomatoes can be broken into two basic groups: determinate and indeterminate. Determinate tomatoes grow to a certain height and stop, thus tending to be smaller and more appropriate for container growing. They also flower and fruit within a relatively short period of time, and all of the tomatoes can be harvested within four to six weeks. Indeterminate tomatoes grow continuously, flower and fruit throughout the growing season, up until the first frost. These plants are much larger and require much more support. Though indeterminate tomatoes can be grown in containers, they can be more difficult to manage and keep healthy.

Whether shopping for tomato transplants or starting plants from seed, try to choose determinate patio or container type varieties. Examples include BushSteak Hybrid, Celebrity Hybrid, Tumbling Tom and Tiny Tim.

Picking a container

Growing healthy, productive tomato plants starts with choosing the right container. Tomatoes have extensive root systems and require a lot of water as the season progresses. Large, four to five gallon containers are usually sufficient for growing individual plants. The material the container is made of is not as important as whether it provides good drainage. If necessary, drill holes along the sides ¼ to ½ inch from the bottom. Though not particularly elegant, a five gallon plastic bucket with added drainage holes is a great size for tomato plants.

Potting Soil

It is always best to grow container vegetables in a quality “soilless” potting mix. Garden soil compacts easily, dries out quickly, yet drains poorly and can contain weed seeds and diseases. Most soilless mixes are composed of a water-holding organic material, such as peat or coir, and an inorganic component that creates pore space/improves drainage, such as perlite or vermiculite. These potting mixes are lightweight, retain moisture and readily shed excess water. Many pre-made soilless potting mixes are available at garden centers, but you can also make your own by combining one bushel each of vermiculite and peat moss, 1 ¼ cups of dolomitic lime, ½ cup of 20 percent superphosphate and 1 cup of 5-10-5 fertilizer. Incorporating some quality compost will add additional nutrients.


Tomatoes grown in containers usually require support to hold them upright. The plants and the fruit they bear can grow quite heavy, and they can potentially bend and break. Trellises and stakes are effective support options. Conical wire trellises with two rings work quite well with most containers and should be enough for most tomato plants. The main challenge with these supports is that they tend to create a humid environment in the center of the plant which can encourage fungal diseases. Spacing containers apart from each other and pruning tomatoes to three or four stems can help.


Proper watering is critical to the success of container grown tomatoes. Tomato plants can be very thirsty, especially as they get bigger and temperatures rise. At minimum, they will need to be watered thoroughly at least once a day, possibly twice. Once the top two inches of potting soil are dry, apply water until it begins to drain from the bottom of the container. Aim to keep the potting mix consistently moist but not soaked. Inconsistent watering can lead to issues like fruit cracking or blossom end rot. Installing a drip watering system on a timer can cut down on maintenance and ensure that plants won’t dry out completely during the heat of the day.


Tomatoes require lots of nutrients throughout the growing season to produce new growth and quality fruit. For a continuous source of nutrients over weeks to months, use a timed release fertilizer according to packing instructions at the time of planting. Two weeks after planting, start using soluble fertilizer once a week. Choose a product that has a higher middle number (phosphorus) than the first number (nitrogen), because while tomatoes need nitrogen to grow leaves, having more phosphorus is important for flowering and fruiting. Tomato fertilizers or 5-10-10 are good choices. Organic growers can instead use a combination of fish emulsion, greensand, kelp meal and bone meal to feed their plants.


The key to harvesting the most flavorful tomatoes is waiting for them to fully ripen on the plant. Tomatoes that are picked early can mature on the countertop, but they won’t have nearly as much flavor or nutrients. Tomatoes that are sold at the grocery store are usually picked long before they are ripe, so that they will hold up better during shipping and last longer on the shelf. You’ll know that the fruit on your plants are ready for harvest when it is fully red (or yellow, orange, green, etc., depending on variety). Once picked, the flavor will be best if the tomatoes are stored at room temperature and eaten relatively quickly. Though, they can be stored in the refrigerator, they will lose some of their taste and the texture may become mealy.


Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.



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Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions.
Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.