A huge spike in complaints about tall grass in Loudoun County prompted supervisors to pass an emergency lawn-mowing ordinance Tuesday — but not before engaging in a heated debate that included the merits of gardening, the definition of a weed and the proper length of a lawn-mower blade.

Under the ordinance, grass on vacant commercial and industrial-zoned property — and houses with less than a half-acre — cannot be longer than 12 inches.