Basically, any heirloom tomato plant will grow in a pot with proper growing techniques, but some are definitely easier to manage than others. The most reliable way to grow heirloom tomatoes in pots, if you are a novice grower, is to start with “Determinate” varieties. Determinate varieties only grow to around 3-4 feet and therefore often don’t require staking and trellising with the pot (whereas “Indeterminate” varieties grow until frost and may get 7-8 feet).
The main difference between determinate and indeterminate varieties, in terms of fruiting, is the timing of fruit production. Determinate varieties will produce all of their fruit over a 2-3 week period rather than continuing to produce throughout the growing season. This doesn’t mean you get fewer tomatoes from a determinate, you just get the crop in a shorter time frame.
This is a breakdown of my personal favorites for container-growing, categorized by Determinate vs. Indeterminate and Heirloom vs. Hybrid:
Favorite Heirloom Determinates for Pots:
- Principe Borghese: A fairly large determinate plant with small egg-shaped fruit that pack a high flavor punch (more acid than sugar). Prolific & great for drying or to use in salads.
- Manitoba: This slicer was developed in Manitoba, Canada, to ripen during the short summers of the Manitoba prairie. Vigorous and early.
- New Yorker: Bush Beefsteak type, yielding 4-6 ounce meaty tomatoes with balanced flavor. Plants set well in cooler growing conditions.
Favorite Hybrid Determinate for Pots:
- Bush Champion: Low maintenance compact plant that grows about 2 feet high, with larger (8-12 oz) tomatoes than most early determinates. Stocky stems that don’t need trellising. This is the one I usually recommend to novice growers that just want to make sure they get tomatoes they can use on their BLTs.
Favorite Heirloom Indeterminates for Pots
Japanese Black Trifele: ‘The fruit color makes this a nice ornamental as well, and the plants are fairly compact as well — one strong stake should support the plant well. Delicious complex, smoky flavor and beautiful bronze color.
- Green Zebra: While considered an indeterminate tomato, they are much less rangy and grow more compactly, reaching about 5-6 feet high depending on your climate. Very poplar for taste, with a tart, slightly lemon background balancing the sugar. A favorite of many for its unique looks also.
- Stupice: Perhaps the earliest heirloom, the plants are compact and the fruit is small, but it produces well all season. Overall, know that early tomatoes tend to not be as flavorable as main season tomatoes. For an early tomato, Stupice is one of the more flavorable ones.
- Paul Robeson: Beautiful, dark purple 3-4″ tomato with intensely sweet and smoky flavor and a juicy, smooth texture. Needs staking, but well worth it. Early
- Other good alternatives include: Eva’s Purple Ball, Gardener’s Delight, Matts Wild Cherry,
Favorite Hybrid Indeterminates for Pots:
- Carmello: Reliable and prolific, with intensely flavorable, 8 oz., juicy red fruits. Disease resistant and a great overall main-season tomato which produces good flavor even during the colder part of the season.
- Sungold: Sweet, prolific and very popular cherry tomato. Most cherry tomatoes will do well in containers, as they grow tall but their fruit is small and they don’t tend to sprawl as much.
Size of Pots for Growing Heirloom Tomatoes:
The bigger the container, the better. Keep in mind that tomatoes grow large root systems, and they need room to develop for best production. A large container will also prevent the soil from drying out too quickly during the heat of summer.
- Minimum size: In general, a 5 gallon container is considered the minimum size. If you use a smaller pot, you are likely to have problems with the potting mix drying out, which can lead to blossom end rot (see this post to help with blossom end rot). The larger indeterminate heirloom tomatoes will grow well in 12-18 gallon containers. A container 12 to 18 inches deep for all tomatoes is generally a good rule of thumb.
- If you are using a container of your own creation, make sure and punch holes in the container bottom to allow excess water to drain properly.
- Be aware of how heavy your containers will be after watering. If you need to move the container to follow the sun, think about buying (or making) a container with wheels under the pot so you can move it around without breaking your back.
- Sun: Keep in mind that tomatoes need around 6-8 hours of sun a day. Try to avoid a really hot afternoon sun if possible.
- Wind: Avoid areas that are susceptible to strong winds. Hot dry winds are probably the most detrimental condition for young plants, causing their leaves to shrivel and die. Strong winds can break the young plants at their growing tips, or topple over and break staked older plants. If you are growing on a deck or balcony you may have to look into some form of protective barrier.
- Staking: If growing indeterminates, place your stakes or cages early and train the plants to grow vertically, allowing as much sunshine as possible to penetrate to the inside of the plants. Secure the stakes or cages well…larger tomatoes can be very heavy.
Soil/Potting Mixes for Pots:
Don’t use soil. Tomatoes grown in containers need a loose, well-drained medium with lots of organic matter. Use a good potting mix rather than potting soil or garden soil. Potting soil can be too heavy for containers, and soil harvested straight from the garden is most likely infested with fungi, weed seeds, and pests.
- Potting medium: Use a high-quality mix containing peat moss and perlite. If preparing your own soil-less medium, blend in a complete fertilizer, either a dry organic product, such as one containing alfalfa meal, bonemeal, kelp meal, or other natural nutrients.
- Compost: I am a great believer in the benefits of good compost. It can add the micro-nutrients that potting soils might be missing and it can aid with drainage and moisture control. I use a ratio of 3:1 soil-less mix to compost.
Fertilizing Container-Grown Heirloom Tomatoes:
- Organic fertilizers: Make a compost tea or manure tea and fertilize monthly during the growing season. Other good organic fertilizers are liquid fish emulsion and liquid seaweed, which can be applied weekly.
- Commercial fertilizers: When you buy your potting mix, you can get one containing slow-release fertilizers, which will help with the growth stages of the plant. Tomatoes grown in containers will usually demand more fertilizer than the initial timed-release fertilizers to carry them through the entire growing season. You may need to add liquid water-soluble fertilizer products to the irrigation water as the season progresses. Follow product directions for concentrations and timing.
- Time-release fertilizers: A popular product for containers is Osmocote Plus at planting time. This is a 15-9-12, time release granular product which is supposed to feed up to 6 months. A fellow gardener, experienced with container plants, recommends following up the Osmocote with Peters 20-20-20 water soluble every 10 days to two weeks.
- Water regularly. Containers dry out more quickly than regular garden beds, and tomatoes are more likely to develop issues such as blossom end rot if they get uneven watering.
- Under-watering: The best way to know if your plants need watering is to check the soil. Stick your finger in the soil and if it is dry an inch down into the soil it is time to water. Containers are above ground and dry out quickly. When the plants are small, water use won’t be as high, but when they are large and setting fruit you will need to water daily. Do not allow containers to dry completely or fine roots will die. Also, if allowed to dry excessively, the potting media will shrink away from the side of the container and will be harder to re-wet.
- Over-watering: As long as you are using a potting mix that drains well you shouldn’t be afraid to water heavily. Good drainage solves most over watering issues. Make sure your containers has drainage holes in the bottom of the pot. Back off the watering a little during fruit set to prevent splitting fruit.
- Type of container: Plastic containers do not dry out as quickly as clay, especially unglazed clay pots. Even plastic containers may require daily watering however, as plants grow larger.
- Self-watering systems: There are a range of self-watering pot systems that can reduce watering maintenance. Probably the best known, and longest trialed of these is the EarthBox 1010039 Organic EarthBox, Terracotta. Although I have never used one, the reports from my customers at the farmers’ markets are all positive. The EarthBox works by wicking moisture out of a reservoir in the bottom of the planter.
- Well Water: occasionally there can be problems from watering with well water. Water from wells is often high in salts or carbonates which can cause problems. One way to prevent excessive salt buildup is to water thoroughly enough to ensure that 10 percent of what is added drains out the bottom. Salt build-up is damaging to plants causing burned leaf edges, stunted growth, and fewer blooms. Along this line, if
saucers are used to catch drained water, empty them to prevent salt buildup.