Omar Flores holds up what appears to be a fluorescent green baseball sprouting a forest of leafy trees. Then he pulls a knife from the braided sheath at his belt and expertly cuts the vegetable into flat rounds.

The newest customer to visit G. Flores Produce on the sandy eastern Virginia peninsula known as the Northern Neck, Tom McDougall, chews the raw, crunchy kohlrabi with an expression of reverence. The plant, an exotic-looking German cousin of the cauliflower and cabbage, would fetch a good price in the cities of Washington, D.C., and Northern Virginia.

“Here's this thing that looks like an alien—and it turns out to grow particularly well in the mid-Atlantic?" McDougall says.

It’s also a bright green representative of the