It's tomato time here in the mid-Atlantic – the critical moment when those of us eager to pull fat, bright fruit off our own backyard vines in a couple months are scurrying to get tender little plants in the ground.
But as anyone who's spent a few summers of kneeling in the dirt can tell you, healthy-looking vines will not necessarily get you a mind-blowingly delicious tomato. And why?
Well, it turns out that scientists still don't know exactly what growing conditions are responsible for the supertasty tomato. But they have a few inklings, which are worth keeping in mind as you try to coax sweetness and tartness from your seedlings.
One scientist who's hot on the trail of what makes a fresh tomato shimmer in your mouth is Harold Klee at the University of Florida. Klee's inspiration to map real tomato flavor began with those pale waxy supermarket tomatoes. You know the ones — they've been bred to travel well and resist pests, but they sure need some help in the flavor department.
According to Klee, good tomato flavor is a complex panorama of sugars, acids, and mysterious gassy chemicals that we experience as smell. Klee and his colleagues are still identifying those "aroma volatiles," and have pinpointed more than 3,000 of them across more than 152 varieties of heirloom tomatoes.
In a paper published last month in Current Biology, Klee says that some of those chemicals can make a tomato taste sweet even though they have nothing to do with sugar.
But he says where and how you grow a plant does influence how it tastes. And gardeners can take heart that access to a greenhouse doesn't mean much when it comes to flavor. "We have always felt that our fruits from the greenhouse, where they are essentially hydroponic, aren't nearly as tasty as those from the field harvested at the same time," Klee told The Salt in an email.
That's probably because the greenhouse tomatoes don't get as much UV light as tomatoes in the field. Which means that the more direct sun you can give your tomatoes the better – and in particular, sweeter — they'll taste.
Too much water can also dilute the flavor. "We know that if you harvest fruit from a plant and then it rains a lot and you go back to the same plant the next day, the fruit tastes less flavorful," says Klee. How much and how often you water depends on how much rain you're getting, but most experts recommend watering two to three times a week in the hottest part of the summer.
Tomato growers in Israel's Negev desert region attribute the sweetness in their fruit to the brackish water they use to hydrate plants. Agricultural extension specialists in New Jersey report that an experiment there using seawater on tomatoes also yielded better flavor.
Just as important, says Klee, is the soil. He recommends planting seedlings in rich soil with lots of organic matter, or compost. And you can add a steady slow-release fertilizer (like Osmocote).
But don't think that a tomato that grows well and tastes like a dream in one place will necessarily thrive somewhere else. That's what author Arthur Allen learned when he tried to plant a tomato he found in California, the Speckled Peach, on the East Coast. The fruit's flavor 3,000 miles away was just mediocre, Allen told NPR.
For expert advice on which tomato breeds are best suited to your backyard, consult your local agricultural extension office.