Biochemical changes in vivo and pathway interactions were investigated using integrated physiological and metabolic responses of Arabidopsis thaliana L. to ultraviolet (UV) radiation (280–400 nm) at 9.96 kJ m⁻² d⁻¹ over the entire life cycle from seed to seed (8 weeks). Columbia‐0 (Col‐0) and a UV‐B sensitive accession (fah‐1) showed significant (P < 0.001) reductions in leaf growth after 6 weeks. Col‐0 recovered growth after 8 weeks, with recovery corresponding to a switch from production of phenylpropanoids to flavonoids. fah‐1 failed to recover, indicating that sinapate production is an essential component of recovery. Epidermal features show that UV radiation caused significant (P < 0.001) increases in trichome density, which may act as a structural defence response. Stomatal indices showed a significant (P < 0.0001) reduction in Col‐0 and a significant (P < 0.001) increase in fah‐1. Epidermal cell density was significantly increased under UV radiation on the abaxial leaf surface, suggesting that that a fully functioning phenylpropanoid pathway is a requirement for cell expansion and leaf development. Despite wild‐type acclimation, the costs of adaptation lead to reduced plant fitness by decreasing flower numbers and total seed biomass. A multi‐phasic acclimation to UV radiation and the induction of specific metabolites link stress‐induced biochemical responses to enhanced acclimation.