How to Grow Tomatoes in Pots

Why grow tomatoes in containers

A pot lets you grow tomatoes on a patio, balcony or driveway, and it solves two common garden problems. Texas A&M and Oregon State both point out that fresh potting mix avoids the soil-borne diseases and nematodes that build up in garden beds where tomatoes have grown before. You can also move the pot to the sunniest spot, or under shelter on a cold spring night.

The tradeoff is water. A pot holds far less moisture than open ground, and Texas A&M expects container vegetables to need watering about once a day.

Choosing the pot

Size is the most important choice. The sources give different minimums:

• Texas A&M and NC State: 5 gallons for one plant. NC State adds a depth of 1 to 2 feet. Texas A&M considers 1 to 2 gallons enough for dwarf tomatoes.
• University of Maryland: 8 to 10 gallons of mix, 12 to 16 inches deep, for full-size tomatoes; 4 to 6 gallons, 8 to 12 inches deep, for dwarf varieties.
• Oregon State: at least 12 inches deep, such as a 5-gallon nursery pot, for determinate types. Plant growth is limited by the size of the container, so a bigger pot gives a bigger plant and a bigger crop.

A 5-gallon bucket works for a patio or dwarf variety. Give a full-size or indeterminate tomato 8 to 10 gallons or more. Put one plant in each pot.

Every pot needs drainage holes. Texas A&M suggests holes along the side, about ¼ to ½ inch above the bottom. The sources disagree about gravel: Texas A&M says an inch of coarse gravel in the bottom improves drainage, while University of Maryland says gravel or pot shards do not help and can leave the bottom of the mix wetter. Both agree that drainage is critical. Raising pots on feet or a brick helps them drain freely.

Material changes how often you water. Maryland notes that clay, ceramic, concrete and wood dry out faster than plastic or metal, and that dark containers can get hot enough to injure young roots. In the hot South and the desert Southwest, a light-colored plastic pot is the easier choice.

Varieties for pots

Determinate and dwarf types take longer to outgrow a pot and are easier to support. Texas A&M recommends Patio, Pixie, Tiny Tim, Saladette, Toy Boy, Spring Giant, Tumbling Tom and Small Fry for Texas container gardens, and notes that small-fruited types make good hanging baskets. NC State lists Tiny Tim as a dwarf patio cherry. Indeterminate varieties can grow in pots too, but they need the largest container you can manage and a tall, sturdy stake or cage.

Potting mix

Do not fill the pot with garden soil. Texas A&M recommends a soilless mix of peat moss, perlite or vermiculite, which drains well, is light, and is free of weed seed and disease. Texas A&M adds that mixes containing compost or pasteurized soil hold water better than purely soilless ones. Wet the mix thoroughly before planting.

Set the transplant deep, as you would in the ground, so the buried stem can root. Put the cage or stake in at planting time. Texas A&M notes that cages work well for container tomatoes.

Watering

Texas A&M finds that watering once a day is usually enough, and that large, leafy plants may need water twice a day in hot weather. Water until some drains from the bottom, so the whole root ball is wet. If the mix becomes waterlogged, roots run out of oxygen and plants yellow from the bottom up, so empty saucers after watering. Keep the leaves dry to limit leaf diseases.

Uneven watering causes blossom-end rot and cracked fruit, so check pots daily rather than waiting for plants to wilt. A layer of straw, compost or shredded bark on top of the mix slows drying. Texas A&M also mentions water-holding gels mixed into the potting mix before planting.

Feeding

Frequent watering washes nutrients out of a pot, so container tomatoes need regular feeding. Texas A&M describes two approaches: mix a time-release fertilizer into the potting mix at planting, or water with a dilute soluble fertilizer as the plants grow, following the label. If you feed with every watering, Texas A&M advises watering with plain water about once a week until it drains freely, to flush out salts. Leaf edges that brown and burn are a sign that salts have built up.

Don’t overdo nitrogen. Tall, leafy plants with few flowers mean either too much nitrogen or too little light.

Sun, heat and cold

Fruiting crops such as tomatoes need the most sun of any vegetable, so give pots the brightest spot you have, with at least 6 hours of direct sun. Texas A&M notes that stunted plants with a purplish color can mean the pot is too cold, so move it somewhere warmer. In cold areas, Oregon State suggests growing tomatoes beside a house wall, where radiant heat warms the plants on cool evenings, and a pot is easy to move there.

At the end of the season

Pick all mature fruit before frost and ripen green fruit indoors. Texas A&M advises discarding the plant and mix rather than reusing the mix next year unless it has been properly composted, because diseases carry over in the mix.