Tomatoes in a Can
By: Beth Marie Renaud
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.
Preparing and Siting the Pot
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.