The Golden Globe nominee, 22, who is known for some of her alternative, new age approach to health and well being, produced a sack of roots at the request of an amused Fallon.
"Every time you come on I always ask you what new things are you doing? Are you drinking a new tea? What herbs do you have? And you went and got me some herbs," the new Tonight Show host, 39, started.
An enthusiastic Woodley happily opened up her bag, pulling out raw ginger and garlic.
"It's winter, right? So it's cold and flu season," she began. "So these are herbs you can find in any grocery store to keep your immune system up."
But when it came time for the horseradish root, the Fault in Our Stars actress whipped out a giant, phallic-shaped root.
"Have you ever seen the actual root before?" she asked as Fallon backed up and covered his eyes. "This is what horseradish looks like in its root form!"
The host continued to shrink back nervously before joking, "I've never seen one this size before. It doesn't look familiar to me at all. Because normally it's grated up, in shrimp cocktail sauce. Shrimp, I'm very familiar with. Almost too familiar with shrimp."
Woodley stunned in a tight black dress and Kurt geiger London Bond pumps.
Expect to see plenty more of Woodley's daring antics as the highly-anticipated film adaptation of the popular YA series Divergent hits theaters on March 21, and the emotionally compelling Fault in Our Stars film adaptation hits theaters on June 6.