A floor seal for a forwardly facing opening through a floor of a plant cutting machine through which a knife arm extends for side to side reciprocating movement for driving a sickle of the machine as the machine is moved forwardly for performing a plant cutting operation. The floor seal includes a stationary outer peripheral seal element engaged with a peripheral edge of the floor about the opening and carrying a cover element in covering relation to the opening about the knife arm and defining and bounding a forwardly facing aperture containing the knife arm and an inner peripheral seal element carried in the aperture by the cover element bounding and forming a barrier to entry of loose material or sealed condition about the knife arm and movable side to side therewith relative to the outer seal and cover.
