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Luke Petersen is a farmer, not a magician.

Yet customers often ask how the Riverton grower turns sweet corn into popcorn.

"I cast a magic spell," he jokes, before politely explaining that the kernels come from a special variety of corn, which when properly dried creates kernels that puff when heated.

At Petersen Family Farms, where Luke is a fifth-generation farmer, three varieties of popcorn are grown: traditional yellow, ruby red and Shaman blue, which has hints of purple. All three varieties burst into white fluffs "that have a sweeter flavor" than store-bought varieties, said Petersen.

These colorful cobs trip people up in several ways. Sometimes they are mistaken for the "Indian corn" used to decorate at Thanksgiving. The kernels also can be popped while still attached to the cob.

Place the whole cob in a paper lunch sack — not plastic— close the top and heat in the microwave for about 2 minutes, or until the popping slows.

Some of the popped corn will break away from the cob, but a "large percent stay on," said Petersen, who grows more than 12,000 cobs a year, along with a host of other produce, including tomatoes, peppers, melons and sweet corn. The market on the farm site recently added new packaging for the popcorn, making it more attractive for customers and for gift-giving. Cobs sell for $1 each.

Popcorn has been around for centuries, with the oldest ears discovered in an ancient cave in west-central New Mexico. Under 2,000 years' worth of accumulated garbage and excrement, anthropologists found cobs, kernels, husks and tassels. Among the prehistoric kernels, there were six that were partly or completely popped.

In America, it wasn't until the late 1800s that popcorn became a valuable crop, bringing in enough money that growers often called it "prairie gold." Today, most of the world's popcorn is grown in the Midwest, namely Nebraska, Iowa and Indiana.

Tyson Roberts, of Roberts Family Farm in Layton, said his father started growing a special variety of corn for popcorn about 20 years ago and selling the kernels to a seed company.

Several years ago, the family decided to sell cobs of traditional yellow popping corn at farmers markets in Murray and South Jordan. "People get a kick out of it," he said, "and it draws people to our stand."

Roberts plants about 1.5 acres of popcorn each year. It resembles grain or sweet corn, but is picked late in the season, usually in November, when the stalk is dried and tipped over in the field. "It's the last thing we harvest," he said.

The husk is removed and the cobs are stored for several months in a large temperature- and humidity-controlled trailer to ensure proper drying and prevent rodent access.

"Popcorn comes out of the field with a moisture content of about 22 to 24 percent," Roberts said. For proper popping, the moisture needs to be reduced by about half. "I like it when it's around 14 percent," Roberts said. "That's when the kernels really explode."

Because of the late harvest and drying process, the popcorn that is being grown this year, won't be sold until next season.

While popcorn is a small part of what Roberts and Petersen grow, both farmers think it's worth the effort. "It's interesting and has educational value," said Petersen. "It helps people know where their food comes from."

Popping it in Utah

Two Utah farmers grow corn used for popcorn and sell it at farmers markets and farm stands.

Petersen Family Farms • 11887 S. 4000 West, Riverton; 801-999-8548. Open Monday-Thursdsay, 9 a.m. to 7 p.m.; Friday, 9 a.m. to 9 p.m.; and Saturday, 9 a.m. to 6 p.m.

Roberts Family Farms • Look for the booth, Friday and Saturday, 9 a.m..- 2 p.m., at Murray Park Farmers Market, 298 E. Murray Park Way; and Saturday from 8 a.m. to 2 p.m. at the South Jordan Farmer Market, 10695 S. Redwood Road.