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Heat and humidity make it hard to grow tomatoes in Florida. Here’s the best way to do it.

An EarthBox planted with two Juliet tomato varieties, before staking.
An EarthBox planted with two Juliet tomato varieties, before staking. Fairchild Tropical Botanic Garden

Northerners know that growing tomatoes is one of the easiest summer gardening goals. Just plant them and wait for sweet tomatoes to appear. It’s not as easy in the Deep South, where heat and humidity create more difficult growing conditions. We do, however, have a brief tomato time in the subtropics, with some caveats.

Plant seedlings too soon in the season, and they’ll rot or fry. Grow them from seeds when it’s still humid and rainy, and they’ll damp off soon after germinating. Try larger transplants, but watch out for tomato hornworms that’ll devour a large plant in hours.

The temptation to try again comes every winter. Others successfully grow tomatoes in South Florida, so why not me?

Before giving up for eternity, I consulted two people who have gotten their hands dirty over the years refining the best methods. Glenn Huberman, a longtime Fairchild volunteer, and Mary Neustein, Fairchild’s manager of adult education programs, both have had luck using an EarthBox, a planter incorporating a water reservoir, fill tube, soil cover, and with other options available like casters. (I’m not promoting or endorsing any product or tomato variety. I’m just experimenting as a fellow South Florida gardener.)

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An EarthBox readied with soil and included fertilizer. Dolomite has also been added. KENNETH SETZER Fairchild Tropical Botanic Garden

One appeal of the EarthBox is there should never be a question on proper watering. The plants can absorb what they want by wicking moisture up from the reservoir without concern that the soil will turn soggy, a condition that would encourage rot. After the initial watering, only the reservoir is filled; the plants are never watered from the top again.

Second, though any pot can be moved, I like the mobility of the casters. Tomatoes will need 6 to 8 hours of sun a day, and in winter that may not be attainable if the plant is in the ground in the wrong spot and immobile.

I’ve previously tried heat-tolerant varieties. Besides the sprawling Everglades tomatoes, I’ve also found some success with Patio Choice Yellow, a plant developed for container growing in small spaces. It’s a determinate variety (stops growth when fruit sets) and was producing tasty, cherry-sized yellow fruit. But just as it started to thrive, stray cats found my yard and knocked the planter over so the poor plant had an untimely demise.

Both growers recommend the Juliet variety of tomato as nearly foolproof (Sweet Million and Garden Gem are also suitable).

Juliet is a Roma/plum, and indeterminate variety, meaning it continues growing, flowering, and fruiting, whereas determinate tomato plants stop growing when fruit sets. Determinates stay smaller, and fruit ripens pretty much simultaneously. Indeterminates can vine themselves to ten feet or so, but Juliet is said to reach about 6 feet. They still require support and pruning near the base to ensure good airflow. An EarthBox will accommodate two of these.

South Florida presents various tomato threats, so look out for sustained high temperatures, especially at night. Humidity affects pollination also; too humid, and pollen is not dispersed sufficiently. Sporadic or sudden excessive watering can cause the fruit to crack, another plus for the reservoir. The other potential problems, like temps and humidity, aren’t as easily overcome.

Blossom drop is a condition that causes the flowers to drop, and of course no flowers means no fruit. Its causes are nearly anything that stresses the plant like high temperatures — especially high nighttime temps — or excessive cold (under 50). Even a delay in pollination can cause blossom drop.

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The enemy: tomato hornworm caterpillar. KENNETH SETZER Fairchild Tropical Botanic Garden

Tomatoes may also suffer a host of other problems. A major threat is from tomato hornworms, which are the caterpillars (larvae) of the five-spotted hawkmoth. Neustein says she hunts for them in early evening, and can hear them chewing! They will defoliate a plant in a matter of hours and then move on to destroy the fruit. Pick them off by hand and throw them to the birds. You may also consider using the natural soil bacterium Bacillus thuringiensis, called “BT. It’s often available as a spray that will kill hornworms before they can destroy your plant.

Blossom end rot is another ailment. If the fruit, especially while still ripening, develops a dark, depressed spot on the bottom, it’s probably end rot. Discard any such fruit right away. Adding dolomite to the soil, preferably before planting, balances soil pH and adds calcium to help avoid blossom end rot.

Back to the Juliets. Mine are planted, are about 2 feet now and staked to a small trellis in full sun. So far they’re fine, though one is a bit weak looking. They should take a couple more months to bear fruit.

Neustein’s optimistic recommendation: When your Juliets are producing loads of tomatoes, cut them in half vertically (they’re oblong), lay them on a sheet pan, sprinkle with a bit of olive oil, salt and pepper and roast them for 45 minutes at 400 degrees. Add them to spaghetti or eat as is.

There are likely as many tomato-growing methods as there are tomato varieties, and there are loads of those, so ask around and do more research as to what techniques and varieties other growers have had success with. Then, hope for moderate temps, cool but not cold nights, and check daily for those hungry hornworms.

Kenneth Setzer is writer and editor at Fairchild Tropical Botanic Garden.