Ratcheting surfaces are a common motif in nature and appear in plant awns and grasses. They are known
to proffer selective advantages for seed dispersion and burial. In two simple model experiments, we show
that these anisotropically toothed surfaces naturally serve as motion rectifiers and generically move in a
unidirectional manner, when subjected to temporally and spatially symmetric excitations of various
origins. Using a combination of theory and experiment, we show that a linear relationship between awn
length and ratchet efficiency holds under biologically relevant conditions. Grass awns can thus efficiently
transform non-equilibrium environmental stresses from such sources as humidity variations into useful
work and directed motion using their length as a fluctuation amplifier, yielding a selective advantage to
these organelles in many plant species.