Growing tomatoes in containers

At a glance

Step by step

1. Pick a compact cultivar

Clemson's Home & Garden Information Center advises avoiding indeterminate types such as 'Better Boy', 'Early Girl', 'Rutgers', 'Brandywine' and 'Cherokee Purple', which keep growing taller until frost. Instead, look for names containing "patio", "balcony" or "bush", which often signal determinate or semi-determinate habits, and check the label's plant height because not every determinate cultivar is compact. Clemson's examples: 'Patio Choice Yellow' (about 18 inches tall, half-ounce yellow cherry fruit), 'Tumbler' (mounded habit suited to hanging baskets) and 'Bush Early Girl' (under 3 feet, round red fruit up to 4 inches across).

2. Choose the container

Clemson suggests a 14- to 20-inch container or a five-gallon bucket with holes drilled in the bottom. UW–Madison gives a 5-gallon, 12- to 18-inch-deep minimum; University of Maryland Extension puts full-size tomatoes in its large class (8–10 gallons, 12–16 inches deep, one plant per container) and dwarf tomatoes in its medium class (4–6 gallons). More soil means more stored water: NMSU's Southwest Yard & Garden recommends a larger container when tomatoes dry out and wilt by evening. UMD warns that dark containers can overheat roots, and NMSU suggests light-colored or shaded pots.

3. Fill with potting mix

UW–Madison recommends a light, organic-rich, well-drained commercial potting mix, ideally pasteurized, plus slow-release fertilizer if the mix has none. Fill the pot completely; do not add a gravel layer, which slows drainage.

4. Plant after frost, with the support in place

Tomatoes are cold-sensitive. UNH Extension lists transplanting 1–2 weeks after the last frost; Colorado State classes tomatoes as "very tender" and plants them two or more weeks after it. Install a cage or stake at planting for anything over two feet, as Clemson advises, so roots are not damaged later. Virginia Cooperative Extension notes that six-foot stakes driven two feet deep suit determinate types and eight-foot stakes suit indeterminate ones; cages made of four-inch mesh allow hands through for picking.

5. Water and feed steadily

Container tomatoes need close moisture monitoring and daily watering in midsummer (Clemson); UW–Madison says the same once fruit sets. Clemson's feeding options are a timed-release pellet fertilizer at planting, renewed per package directions, or a water-soluble fertilizer once a week.

Blossom end rot in pots

Blossom end rot affects the blossom end (bottom) of the fruit. NMSU's Southwest Yard & Garden explains that it is caused by a lack of calcium at the blossom end of young fruit, and that in many gardens the problem is not missing calcium in the soil but drought stress: calcium moves through the plant in water, so when a plant wilts, delivery to the fruit fails. Affected fruit cannot be fixed. Prevention focuses on keeping plants from wilting: larger containers with more soil volume, morning sun with afternoon shade in hot climates, light-colored or shaded pots, and watering before plants dry out.

Common container mistakes

• Choosing an indeterminate heirloom for a small pot (Clemson).
• Using a container too small, which forces "constant watering" (Clemson).
• Adding gravel at the bottom (UW–Madison) or using a dark pot in full sun (UMD).
• Waiting to cage until the plant sprawls (Clemson: install support at planting).
• Setting plants out too early; check your frost date and the planting calendar.