Macrophytes are emergent, submerged or floating aquatic plants. Macrophyte growth in rivers is typically patchy, but experimental work has tended to focus on large, uniform, stands of vegetation. Blockage caused by patches significantly elevates water levels and influences mean and turbulent flow fields; conversely, mean and turbulent flow fields influence the location and form of patches. Herein, we utilise infrared photography, repeated at a rate ranging from monthly during the dormant season to biweekly during the growing season, to investigate spatio-temporal patterns of growth, die-back and regrowth of the in-stream macrophyte Ranunculus penicillatus ssp. pseudofluitans (Syme) S.D.Webster. Ranunculus p. forms patches that are commonly rooted only at their upstream edge, while its long flexible stems (0.3-2.0 m) and leaves trail downstream. Image analysis indicates that patches that are removed through quarterly management activities reform in similar locations within several weeks, whereas within the annual cycle, patches tend to die back and reform in different locations. However, in both scenarios, patches tend to have similar forms (with a consistent streamwise to cross-stream length ratio), orientations (with their long-axis parallel to the channel banks), size distributions and fractal dimensions. Velocity measurements suggest that, dependent on the shape and size of patches, the local flow regime changes throughout the growth cycle. The growth of small patches from a previously bare bed causes a large change to the rate and propagation of turbulent structures, while continued growth and amalgamation has a greater impact upon the form of the mean velocity profile and form-induced stresses.