Abstract: A seeder apparatus comprises a seeder plate (18), which is hingedly attached at a hinge edge (70) thereof to a frame (16), with the frame being mounted on a plug-tray conveyor (12). The seeder plate includes a substantially-flat seeder sheet (36) having seed holes (38) therein and a pressure-plenum (48) on a backside (41) of the seeder plate for producing negative and positive pressures at the seed holes. Hinges (20) are double-acting, spring-loaded barroom type door hinges which bias the seeder plate toward an upright intermediate position which is approximately halfway through 180.degree. movement of the seeder plate between an approximately horizontal loading position and an approximately horizontal planting position. The seeder plate includes a vibrator (54) for automatically vibrating it and an angular-activation adjustment element (60) for adjusting the angular positions in which this vibration takes place.