If your garden is too small for full-size tomato plants, or if your soil is plagued by fungal diseases or nematodes, don't despair. Do as Jim Wilson -- co-host of the Great Gardeners Program on HGTV, and former co-host of The Victory Garden on PBS -- does, and grow tomatoes in containers big enough to hold indeterminate varieties (those that continue to vine even after initial fruit set) with full-size fruit. Every year, from two plants per container, he harvests about 60 pounds of ripe tomatoes. A wire cage around each container supports the plants as they grow.
Choose a container with a capacity of 25 to 30 gallons; durable plastic or a whiskey half-barrel works well. Wilson's choice is a plastic garbage can. If you live in a hot-summer area, use a light-colored container that won't absorb the sun's heat and burn the plants' roots. Don't use any container made of metal; it will get too hot for good root growth and may contain zinc, which, at high concentrations, is toxic to plants.
One major advantage of growing in containers is that you can keep plants free of common soilborne fungal diseases: verticillium and fusarium wilt. A soilless potting mix -- purchased or homemade -- provides a nearly sterile environment for the plants. Three 40-quart bags of soilless potting mix are ample. If you want to make your own, mix 50 percent bark soil conditioner -- use pine bark in the East and fir in the West (soil conditioners are bark ground finer and aged longer than for mulches); 35 percent peat moss; and 15 percent perlite. Do not add compost to the soil or line the bottom of the container with rocks; both may introduce disease to the potting soil. Additionally, Wilson recommends mixing 1 ounce of pelletized dolomitic limestone per gallon of potting mix to protect against blossom end rot, which results from a deficiency of calcium and magnesium. In the arid West, where the pH in soil is naturally high and limestone is not readily available, treat plants that develop blossom end rot with a solution of 1 tablespoon Epsom salts per 5 gallons of water.
For proper drainage -- and to avoid the root rot that can result from perpetually wet roots -- drill six 1/2- to 3/4-inch-diameter holes into the bottom of the container. Cover the holes with window screen to prevent soil from washing out. Then, to keep the container out of contact with the ground, which can contain soilborne diseases, set it on four bricks.
Tomatoes need at least 6 hours of sunlight each day, and they produce best with 8 hours. Set your container in a sunny spot, preferably with a hose nearby for easy watering. If you live in the South where summers are hot, position pots where plants can benefit from afternoon shade. Where daytime temperatures exceed 90° F and night temperatures exceed 70° F, the pollen on the tomato blossoms can become sterile, ceasing or deforming fruit production. The afternoon shading helps minimize this condition and will also keep the soil from drying out too quickly.
Once the container is in place, fill it to within 2 inches of the top with soilless potting mix. Mix a controlled-release fertilizer into the top 3 inches of soil to feed the plants through late summer. If you live in an area with an extended growing season, you may have to supplement feedings with a water-soluble fertilizer (at the recommended rate) when growth slows in late summer. For an organic option, feed plants twice a week with fish emulsion.
The size of the container allows you to grow any full-size indeterminate variety. In each container, set out two transplants (with six to eight leaves each), preferably disease-resistant hybrids such as 'Big Beef' or 'Better Boy'. Look for varieties with the code letters VFNTA; these signify their resistance to verticillium and fusarium fungal diseases, nematodes, tobacco mosaic virus, and alternaria leaf spot. In the South, try heat-tolerant varieties such as 'Arkansas Traveler' and 'Tropic'. Where the growing season is short, you may want to use strong determinate varieties such as 'Celebrity' and 'Solar Set', because they will fruit earlier, or try early-fruiting indeterminate varieties such as 'Early Pick' and 'Stupice'.
After planting, water transplants well, then set up a cage to give them support as they grow. Measure the circumference of the rim of your container. Cut an 8-foot-wide piece of steel reinforcing wire to the size of the circumference plus 6 inches for overlap. Use wire with 6-inch holes so you can easily stick your hands into the cage to water and prune the plants and harvest the fruits. Wrap the cage around the container with the lower edge on the ground, then secure the cut ends with wire. For support, drive two steel fence posts into the ground next to the cage and attach them to the cage with wire.
If you set out your plants early in the season, wrap two layers of clear plastic around the cage and fold it over the top, leaving an air hole for ventilation. Remove the plastic when daytime temperatures average 70? F.
Water plants when the top 3 to 4 inches of soil are dry. Avoid wetting the foliage, and soak the soil until you see water draining through the bottom of the container. After the plants begin to set fruit, water them daily, especially on hot, windy days.
When branches extend beyond the cylinder, tuck them back inside. If you live where summers are hot, don't prune the plants; they need to develop foliage to shade the fruit from strong sun. In cooler regions, pruning will help maximize fruit production. Pinch back suckers as they grow, and prune the tips of growing stems late in the season, removing buds that won't have time to bloom. Also remove fruit before the first frost and either eat them as green tomatoes or ripen them indoors by wrapping the fruits in newspaper and keeping them in a 70° F room.
If an early frost threatens to stall tomato production, Jim Wilson recommends covering the cylinder with an old blanket. Lifting it on and off with two long hoe or shovel handles helps to minimize damage to branches and fruit.
After setup and planting, keep soil evenly moist. Later in the season, once plants are large, this likely means watering every day.
1. A 25- to 30-gallon container is large enough to support two full-size tomato plants. Place it in full sun, or where plants receive at least 6 hours of direct sunlight a day.
2. Elevate the container above the soil to facilitate drainage and prevent disease organisms in the soil from reaching tomato roots.
3. Fill container to within 2 inches of rim with "soilless" potting mix, either commercially prepared or homemade.
4. Plant two tomato seedlings such as 'Celebrity' or 'Better Boy' (or one of each).
5. After planting, wrap the container with a section of 8-foot-tall steel reinforcing wire that has 6-inch openings. Measure the circumference of your pot first, and add about about 6 inches for overlap. Most pots need a piece about 8 feet long. Hold the ends in place with small wire ties.
6. Secure wire with two 8-foot-tall steel fence posts tied to the wire in at least two places.
Beth Marie Renaud is a former executive editor at National Gardening.
Photography by Sabin Gratz/National Gardening
Article published on June 23, 2008.