STARKVILLE, Miss.—Over the past hundred years, the George family’s farm has been sharecropped, grazed by cattle and planted with cotton. By the late 1980s, Clayton George was growing soybeans and struggling to make ends meet.

A new federal program offered farmers money to reforest depleted land. Pine trees appealed to Mr. George. He bought loblolly seedlings and pulled his pickup into a parking lot where hands-for-hire congregated.

“We figured we’d plant trees and come back and harvest it in 30 years and in the meantime go into town to make a living doing something else,” he said.

Three decades later the trees are ready to cut, and Mr. George is learning how many other Southerners had the same idea.

A glut of timber has piled up in the Southeast. There are far more ready-to-cut trees than the region’s mills can saw or pulp. The surfeit has crushed timber prices in Mississippi, Alabama and several other states.