Abstract: There is provided an inter-plant arm assembly for selectively mounting a predetermined number of additional planter units to a multi-row planter having a plurality of existing planter units. The inter-plant arm facilitates quick and efficient varying of row widths to plant different crops. The inter-plant arm includes a front arm that attaches to the planter adjacent an existing planter unit and extends at a predetermined angle of incline and a rear arm that carries at least one additional planter unit. A coupling between the front and rear arms allows for quick attachment and detachment of any desired additional planter units. The coupling defines a receiver that accepts an end portion of the rear arm and includes a pin and lock to selectively secure that end portion of the rear arm in the receiver.