Growing Tomatoes in Containers

Container Tomatoes

Growing healthy, productive plants in pots

Growing a good healthy crop of heirloom tomatoes in containers was challenging for me for a lot of years. I can grow healthy sturdy seedlings like nobody’s business but I got inconsistent results with mature fruiting plants. Through trial, error and some key observations I feel like I’ve conquered the major hurdles and can give some advice. Here goes.

Example of 20 gallon fabric pots. These are by Dirt Pot.

The Container
• You need a large one. 20 gallon minimum for ONE tomato plant. No compromises here! 25-30 gallons is even better. Remember, Roots = Shoots + Fruit. Smaller volume containers will limit your plant and make it more stress prone. The exception to the 20 gallon rule is varieties that are bred to be super small, like Whippersnapper.
• Fabric pots are the best choice. They work well because they breathe, buffer hot temperatures and encourage a dense mass of fibrous roots that naturally air prune as they grow to the edge of the pot, unlike roots in a hard container that circle the inside and become choked and rootbound. Fabric pots, especially the lighter colored ones, are less likely to overheat the root zone and stress your plants. There are many brands out there--Dirt Pot, Smartpot, Root Pouch, etc. I chose Dirt Pot because they are made from recycled materials and are sturdy. They are very inexpensive, washable, reuseable, and are easily folded and stored. They will discolor as the season wears on, no matter what color you choose.

Potting mix should be moist, fluffy, deep brown and with a medium texture

The Soil
• Use an organic potting mix. Not garden soil, not compost. While I can’t name a preferred brand, as I don’t typically buy bagged mixes, look for mixes that include beneficial microbes, humic acid, worm castings, a variety of nutrient sources such as fish/feather meal, kelp, bone meal, etc., and replaces at least some of the peat moss with coir. Based on the ingredient list, E.B. Stone’s Ultimate Recipe and Recipe 420 both look good. Once you open the bag, it should be moist and fluffy with a medium texture and a deep brown color. It shouldn’t be all fines with a bit of perlite, nor should it have a lot of coarse woody material. It should smell earthy, not like rotting garbage or overwhelming ammonia.

Planting
• Plant deeply. As I suggest with all tomato plantings, you want to plant your tomato deep, so deep that you bury ½ or more of the stem. Don’t worry, the buried stem will produce roots very quickly and you’ll then have a healthy, more productive plant. Clip off the leaves from the lower ½ of the plant and dig a deep enough hole in your potting mix that the naked stem can be buried. Gently loosen the root mass so that you lose the shape of the nursery pot and place the plant in your hole. Fill in with potting mix and don’t tamp it. As you water the mix will compact itself appropriately. Water thoroughly 3 times, waiting a few minutes between each watering.

Feeding
• At planting time, mix 2 handfuls of an organic fertilizer such as Down-To-Earth’s All Purpose 4-6-2, a handful of fish meal (not fish bone meal), a handful of pure worm castings and 2 crushed eggshells into the upper ⅓ of the container. When you make your planting hole, throw a couple of plain aspirin in the bottom of the hole.

• Feed frequently. Container plants will go through nutrients quickly, so you need to feed every 3-4 weeks if using a dry fertilizer, or once per week if using a liquid. Nitrogen is the most volatile nutrient, so replacing that consistently is important. Use your fish meal and a handful of worm castings at each feeding. Work the ingredients into the top few inches of soil and water well.

Watering
• Not too much! Tomatoes do not like to live in constantly wet soil, they like to dry between waterings. Your new seedling in a big pot in the spring will need far less water than it will when it’s a big plant in the summer heat. You’ll have to get a feel for how quickly the soil is drying. Poke a hole in the soil and reach your fingers down several inches. If it’s moist, don’t water! If your tomatoes get brown and mushy on the bottom, that’s often a sign of inconsistent watering or stress. Get into a routine and continue to check moisture as the season wears on.

Caging
Don’t forget, your tomato plant needs a big cage! Unless your plant was bred for small size, it’s gonna get way bigger than those flimsy inverted cone-shaped cages can handle. Invest in a tall sturdy cage or make your own. I like a 6’ tall cage.

Other thoughts
Where you place your container is important. A south/west facing wall or a hot, dry patio can reflect an excess of intense light and heat that will make life difficult for your plant. Avoid extremes if you can. If you’re growing plants in several containers consider grouping them together loosely so that they can help protect each other from the intensities of summer. If your tomato plant starts looking stressed when the long, hot days are here, you can drape some shadecloth or burlap around the lower 1/4 of the cage and the container to buffer some of the UV and heat hitting the pot and lower plant stem.

I hope this helps you have a successful container garden. Happy growing!