A rotary cultivator comprises a central gearbox (1) driving a vertical tool shaft (6) and horizontal tool shafts extending from each side of a central pinion (12). The tools carried by the vertical shaft (6) have a working diameter greater than the space between the tool tools of the two horizontal shafts. The outer ends of the horizontal shafts are foldable about vertical axes for road transport of the cultivator. The gearbox (1) comprises interchangeable pinions (8, 9) for obtaining different speeds of rotation of the tool shafts. The outer ends of the horizontal shafts are supported in ball-bearing carried by vertical arms depending from a transverse member (23).