In Bouvardia ‘Van Zijverden’ flowers held in deionized water leaf wilting started from day 6 of vase life, while flowers placed in tap water did not show any leaf wilting for the 14 days of the experiment. Fresh weight of chrysanthemum ‘Cassa’ flowers started to decrease after three days in deionized water. In a solution of major tap water components (0.7mM CaCl2 1.5mM NaHCO 3 0.005mM CuSO 4 ) fresh weight of the chrysanthemum flowers did not decrease within the 7 days of the experiment. CuSO 4 alone, or a mixture of CaCl2 NaHCO 3 did not have this positive effect on fresh weight. However, none of three rose cultivars (Madelon, First Red, Frisco) showed a difference in fresh weight during vase life between deionized water or the solution of CaCl2 NaHCO 3 CuSO 4 . When copper was replaced by AgNO 3 or DICA fresh weight of chrysanthemum did not decrease within the 7 days of the experiment, while it decreased from day 2 when only CaCl2 NaHCO 3 were present in the vase solution. Bouvardia flowers in AgNO 3 dissolved in deionized water did not show any leaf wilting, while all stems of flowers placed in NaNO 3 or deionized water did. The relevance of deionized water as control treatment in vase life experiments was questioned. It is proposed to use a solution of CaCl2 NaHCO 3 CuSO 4 as ‘standardized tap water’.