Spiral root is a common occurrence in tobacco float beds. Almost all trays have a few spiral roots, but typically less than 2% of all cells in a tray are affected. Higher incidences have been observed under certain conditions.

Though the exact cause of spiral root is not known, it it thought to be the result of damage to the tender root tip of the seedling early in germination as it attempts to break out of the seed coat and pellet. Rapid drying at the media surface leading to firmer pellets has been associated with high incidences of spiral root. One specific type of pellet was often associated with very high incidences of spiral root and is no longer used in tobacco float systems.   

Information on managing spiral root can be found in the transplant production chapter of The Burley and Dark Tobacco Production Guide.