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Burger King's plant-based Impossible Whopper is taking root in three new markets, Restaurant Brands International  (QSR - Get Report) said Tuesday.

After a test run in St. Louis, the Toronto-based company said it was introducing the burger in Miami; Columbus, Georgia; and Montgomery, Alabama. 

The Impossible Whopper consists of a flame-grilled patty made from plants topped with tomatoes and onions,  lettuce, mayonnaise, ketchup and pickles on a toasted sesame seed bun.

To mark the occasion, Burger King will have a tour bus go through the three locations. The tour starts in Miami, May 16-18, then on to Columbus May 20-21, and Montgomery on May 22.

Restaurant Brands International wasn't active in premarket trading, but it closed Monday down 2.4% to $65.83.