Pumpkins and gourds covered in warts are popping up in pumpkin-picking patches and farmers stands across the country this fall. What's the story behind these peculiar pumpkins?

No, it's not a hideously disfiguring disease that's suddenly stricken one of America's favorite autumn staples – these pumpkins have been genetically engineered to look that way.

It takes at least 10 generations of cross-breeding to produce a pumpkin that's adequately covered in warts to be sold under the Super Freak label, according to Roy Pearman, director of sales and marketing for Siegers Seed Co., based in Holland, Mich., which "puts the genetics together" to create seeds for the bumpy, heavily wart-covered pumpkins and gourds.

[Images: See pictures of warty pumpkins]

"These wart characteristics have always been around, but we're the only ones to have bred them to cover large areas of the pumpkins," Pearman told Life's Little Mysteries.

Super Freak pumpkins and gourds have been growing in popularity this autumn, according to Pearman. Although the unusual-looking pumpkins have been on the market for three years now, this is the first year they have been sold so widely and marketed so heavily.

Siegers' latest creation, Knuckle Head Pumpkins are the only warty pumpkins genetically designed to be 12 to 16 pounds (5.5 to 7.5 kg), bred larger specifically for the purpose of being carved into especially eerie, ghoulish jack-o'-lanterns.

Normally, a pumpkin with even one wart is viewed as defective, and gets ignored by choosy shoppers, but Pearman said Super Freaks have been especially popular this year, and he expects demand to continue to grow as Halloween approaches.

"It's a special pumpkin," Pearman said. "It's odd and unique, and everything odd and unique is very desired."

This article was provided by Life's Little Mysteries, a sister site to LiveScience.