(NEXSTAR) — A stinky but handsome and widely popular landscape tree has become an aggressive invader.

Callery pear trees create dense thickets that overwhelm native plants and bear four-inch spikes that can flatten tractor tires. The stench wafting from their blossoms has been compared to rotting fish, chlorine or a cheese sandwich left in a car for a week.

Missouri’s Department of Conservation is holding a buyback program for the tree, NewsNation local affiliate KOLR reports. To qualify, a property owner must provide a photo of a cut down pear tree in order to earn a free, less offensive replacement tree.

Other states have taken action against the tree, too. Pennsylvania’s Department of Agriculture has decided to place a phased ban on the Callery Pear, giving nursery owners time to draw down their inventories. About 12 Midwestern and Western states have reported invasions of the plant, though most are in the South and Northeast.

Bradford pears and other ornamental Callery pears were cultivated from an import that saved pear orchards from a deadly bacterial disease. And for decades, the decorative trees seemed near perfect, aside from a tendency to fall apart after about 15 years — and their smell.

But then, they cross-pollinated with other ornamental varieties.

Invasive stands now have been reported in more than 30 states. Fourteen states have formally listed the trees as invasive.

Their invasiveness stems from their adaptability; callery pear trees’ bug-resistant, waxy leaves mean insect-eating birds don’t come near them.

The Associated Press contributed to this report.