This paper compares two marshes of contrasting sedimentology at Tillingham marsh, eastern England, and Warton marsh, North West England. Soil shear strength and compressibility are determined by applying geotechnical methods to determine marsh resistance to shear- and vertical effective- stresses. This research was able to isolate the influence of roots on substrate shear strength in a three-dimensional sample. In response to vertical effective stress, both the expected displacement magnitude and the vertical recovery potential of a marsh substrate are affected by past stress conditions on the marsh, particularly those resulting from desiccation. The substrate response to vertical effective stress also influences substrate shear strength through the effect of consolidation on the void ratio (or bulk density).