Three ornamental bromeliads, i.e. Aechmea ‘Maya’ (CAM), Aechmea fasciata ‘Primera’ (CAM) and Guzmania ‘Hilda’ (C 3 ) were grown under greenhouse conditions at ambient (380ppm) and elevated (750ppm) CO 2 . The effects of long-term exposure (34 weeks) to elevated CO 2 on growth and morphological traits constituting the ornamental value were assessed.Aechmea ‘Maya’ and A. fasciata ‘Primera’ showed a different growth response to elevated CO 2 exposure. Aechmea ‘Maya’ showed for both CO 2 concentrations an equal biomass enhancement throughout the experimental period. In accordance leaf micromorphology remained unaffected. For A. fasciata ‘Primera’ CO 2 fertilisation led to a decreased biomass production (25% less fresh and dry weight) due to a reduced total leaf area (41%) and lower leaf thickness (9%). These responses of both Aechmea hybrids are quite uncommon for CAM plants.Doubling the atmospheric CO 2 concentration stimulated growth for Guzmania ‘Hilda’ shown by an increase in total leaf area (34%) and leaf thickness (11%). However, the surplus in biomass production (57% more fresh weight and 69% more dry weight) was gained only in the first 22 weeks of the experiment as afterwards acclimation occurred.For all three bromeliads elevated CO 2 exposure led to adverse effects on the ornamental value. Leaves from high CO 2 grown plants displayed a visual paler green colour than leaves from control plants due to halving of the total chlorophyll content. Furthermore, allometric relations changed between leaf length and leaf width causing a more compact plant shape. This ultimately resulted in the loss of the typical plant shape for ornamental bromeliads with long and slender leaves.Overall the results in the current study show that long-term exposure to elevated CO 2 does not always lead to enhanced biomass production. Moreover it can lead to adverse effects on the ornamental value. Thus, it is apparent that caution is needed with the application of CO 2 fertilisation in commercial ornamental cultures. The CO 2 plant response can seriously differ among individual species in one family and even in one genus. Therefore it is important to realise that the study of only one representative for a certain plant family or a genus is not adequate to make the proper interpretations concerning general CO 2 responses!