Supporting tomatoes in containers and grow bags

Tomatoes grow well in pots, but a pot makes support harder. There is less soil to hold a stake upright, the container itself can blow over, and a tall plant puts a lot of leverage on a small base. A few adjustments make the difference.

Start with the pot

For one tomato plant, use a container that holds at least 5 gallons of potting mix. Vining varieties do better in 10 to 20 gallons. A bigger pot holds a support more firmly, dries out less quickly and is harder to tip.

Heavy materials help in exposed spots: glazed ceramic, concrete or a plastic pot set inside a heavier outer pot. A light fabric grow bag is easy to move but can lean once the plant is tall. If you use one, plan to anchor it, as below.

Choosing a support for a pot

Bush and patio varieties

A compact determinate or dwarf plant can often get by with a small cage or a short ladder. Push the legs right to the bottom of the pot so they rest on the base instead of floating in the mix.

Vining varieties

A tall plant in a pot needs a support that reaches the bottom of the container and is tied to something solid above. Some options:

• A stake pushed to the bottom of the pot and tied at the top to a railing, fence or wall hook.
• A ladder or obelisk with legs that sit on the base of the pot.
• A string run from a hook overhead down to a loop around the base of the plant, which you wind the stem around as it grows. This works well on a balcony or in a greenhouse.

Install it before you fill the pot

If you can, put the support in the empty container first, then add the potting mix around it and plant. The mix holds the support more evenly, and you won't break roots pushing a stake down later. A stake set this way should be centered, or slightly off-center toward the side where the stem will go.

Stopping the pot from tipping

On a windy patio or rooftop, the pot and plant act like a sail. To keep it upright:

• Group pots together so they shelter each other.
• Place them against a wall or railing and tie the support to it.
• Add a layer of gravel at the bottom only if you also have drainage holes; it lowers the center of weight.
• Turn the plant now and then if it's leaning toward the light.

Care through the season

Potting mix dries quickly, and a plant that wilts and recovers each day puts strain on its ties. Water regularly, more often in hot weather, and check the ties when you do. Loosen any that are getting tight.

Prune vining varieties to one or two stems, as you would on a stake in the ground; the method is in tying and pruning a staked tomato.

Where to go next

Gardener's Supply and most garden centers sell short ladders and cages sized for pots. Check the leg length against the depth of your container before you buy.