The cost of reproduction hypothesis assumes that current reproduction decreases future growth, survival and/or reproduction. To reduce the reproductive cost, contribution of photosynthesis by reproductive organs has been reported. This study tested the cost of reproduction in a spring ephemeral plant Gagea lutea (Liliaceae). We designed the study to find out reproductive cost by examining the annual changes in bulb size. Daily carbon fixation per plant and the importance of leafy bracts were also assessed. These experiments were carried out under open and forest habitat among (1) reproductive intact, (2) floral-bud removal, and (3) bract removal plants. Bulb growth decreased significantly by flower and fruit production in both habitats. Bud removal plants fixed significantly lower carbon than intact plants in the open habitat. In addition, bracts of intact plants fixed significantly larger carbon than bracts of bud removal plants under the forest. This shows the ability of bracts to support reproduction under shaded condition. Furthermore, bract-removal treatment significantly reduced the seed number and seed mass in both habitats. This reflects the importance of current photosynthesis by bracts for seed production and explains why this organ is present only in reproductive individuals.