Jane Zhang:

In a cramped shop filled with stale aromas of Chinese herbs, Keary Drath, a stout Wisconsin farmer and self-appointed ginseng sleuth, picked up a dry, wrinkly ginseng root, broke it in half and chewed it.

Clerks and customers of Ginseng City Trading Inc., stopped haggling in their rapid-fire Mandarin and stared. “From China,” he declared. “Not Wisconsin.”

“What’s the difference?” asked a shocked customer, Max Chen, who has used ginseng for 20 years. “They all say it is Wisconsin ginseng. I know Wisconsin’s is superior.”

Mr. Drath, 42 years old, wishes he had an easy way for Mr. Chen and millions of other ginseng buyers in Asia and in Chinatowns all over the world to make the distinction. The future of Wisconsin’s century-old ginseng farming business, now under attack by global rivals, depends on it.

The root has been worshiped as an energy-balancing folk medicine for 5,000 years. Ginseng — or Ren Shen, meaning “Man Root,” in Chinese — has two types. American ginseng (Panax quinquefolius) has a cooling effect. Asian ginseng (Panax ginseng) provides a hot rush of energy.

With its rich loam, sunlight and cool summers, Wisconsin — especially Marathon County in the central part of the state — produces premium American ginseng. It is more potent and more bitter than American ginseng grown elsewhere.

To an untrained eye, dried Wisconsin roots look the same as those produced in great quantity in Canada and China. Mislabeling and product mixing abound.

And that is threatening the livelihood of Wisconsin’s ginseng farmers, whose roots trace back to the early 1900s when the four Fromm brothers began cultivating ginseng in Marathon County. Ginseng isn’t easy to cultivate: It takes four to five years to grow ginseng under wood or fabric canopies.

“Kids are easier to raise than ginseng,” says Stephen Kaiser, 59, of Rozellville, Wis., who has been grown ginseng since 1977. “Kids only get colds, flu or pneumonia, but ginseng, it tends to die very easily.”