Naturally evolved plant hygroactuation mechanism involves an optimised capillary system for fast liquid distribution in a swellable cellulose fibrous anisotropic structure, which is a source of inspiration for the design of efficient hydromorphs. In particular, the relative contributions, mobility, and transition kinetics of free water contained within the capillaries and water bound to the cellular walls are crucial optimisation parameters in engineering systems based on controlled internal swelling agent dislocation. We introduce a methodology to detect free water accumulated in the centre of the awn based on internal light scattering. Free liquid transfered across the awn half-thickness (32 μm) in 24 s, evidenced by decreased light scattering. Optical scattering data was compared to swelling kinetics, expressed as awn (un)coiling, that primarily associates with bound water. After stopping the water influx, the awn proceeded uncoiling for approximately 12 s due to highly mobile free water still reservoired in the capillary structure. The insight into internal water rearrangement kinetics in awns allows the design of more efficient anisotropic robotic systems that actuate and change stiffness by combining internal liquid displacement and liquid exchange with the environment.