To grow tomatoes in containers, consider final plant size and how often you’ll water – The Virginian-Pilot

Q. What size container, and potting mix, would you recommend for growing tomatoes? — B. Axson, Chesapeake

THE. While there are many benefits to growing in containers, the biggest drawback is water retention. A tomato planted in the ground, or even in a raised bed, has the luxury of spreading its roots far and wide in search of water and nutrients. Container-grown plants have a finite amount of media, defined by the container size, in which to spread their roots. The mix must be able to hold enough water to fulfill the plant’s needs between waterings.

You will see various recommendations for pot sizes — 18 to 24 inches in diameter, 1 to 5 gallons, no smaller than 5 gallons, and so on.

Your selections depend, really, on two things: the ultimate size of the plant, and how often you are willing, and able, to water it.

One factor in the ultimate size of the plant is its genetics.

Determinate tomatoes tend to be bushier, shorter and shorter-lived. Indeterminate tomatoes run up and just keep on growing. It makes sense that the former might do OK in a smaller pot, while the latter could require a larger one. If your rationale for growing in a container is to save space, the determinate type is the way to go. (The plant will also be easier to train and keep in bounds.) You should be able to find the type of tomato you want to grow — cherry, slicing, sauce — in either form.

As for the type of media to use: Rather than a mix that is mostly peat, look to use one that is tighter, which will hold more water. By “tight,” I mean a mix that has small particles, and thus smaller pores, that hold water. As I’ve written before, there are so many of these mixes out there. It can be confusing. You may have to experiment to find the one with just the right balance for your plant type, container size and sun exposure.

In my experience, a 15-gallon container is the minimum size for me. I am not particularly concerned with aesthetics, so I use nursery containers — the black ones that nurseries use for trees and shrubs. These are 18 inches in diameter and 15 inches high. This size requires slightly more than 2 cubic feet of mix to fill — all the way to the top (important).

Loose, predominantly peat, mixes tend to dry out quickly and can be difficult to re-wet. Always water thoroughly and watch for channeling of the water down the sides of the pot. A layer of composted grass clippings helps to reduce evaporation and reduce compaction. Nevertheless, at the end of the last growing season, I had a 20% shrink of the potting mix — even with careful watering.

Cages made from concrete-reinforcing wire fit nicely around the pots and help keep the plants under control. These are sturdy and long lasting, well worth the time and money.

I grow a combination of determinate and indeterminate types. It’s not unusual for these to need watering daily, or at least every other day, during the hottest days of summer. If I am out of the area, I must enlist a friend to fill in. (If creative, one could rig up a self-watering drip system.)

Keeping container tomatoes watered can be a challenge, but it can be done. Add a bit of luck and your container plants will reward you with an abundance of these must-have summer fruits.

And one more thing (or two)

A couple of weeks ago, I was scurrying around, trying to cover my tomatoes from the threat of hail and wind overnight. Then came a coastal low that lingered offshore for several days, bringing strong winds and less than seasonable temperatures. All of this followed a couple of cold spells in April. No question the weather has been less than optimal for the spring garden. Anyone ready for summer?

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