Hierarchical flower-like H₂Ti₅O₁₁·3H₂O assembled with radial nanowires was fabricated via a template-free solution-based reaction, and was converted to TiO₂ with distinct phases and morphologies by the subsequent acid-treating or annealing. The HCl treatment achieved the controllable conversion from titanate nanowires to rutile nanorods by varying the temperature and acidity. When compared with the as-synthesized titanate nanowires and the thoroughly transformed rutile nanorods, their mixtures were found to exhibit the best dye adsorption ability towards rhodamine B and methylene blue in water. The H₂Ti₅O₁₁·3H₂O nanowires decomposed in sequence to anatase and rutile after a subsequent calcination in air, via an intermediate phase of H₂Ti₄O₉·H₂O. The hierarchical structure could be retained up to 800 °C. When utilized as photocatalysts to degrade rhodamine B in water, the 550 °C-calcinated powder, with mixed phases of anatase, rutile, and srilankite, demonstrated the highest photocatalytic activity.