Hmmm... if your plant is Yucca filamentosa or Adam's Needle, one of the more common Yuccas and tolerant of cold temperatures, it will bloom each year after reaching maturity. If sown from seeds it will take 6 or 7 years to reach maturity in order to bloom... Additionally, this genus is set apart from other flowering plants in that their method of pollination is quite unique: A specific moth that is genetically programmed for stuffing a little ball of pollen into the cup-shaped stigma of each flower. Like fig wasps and acacia ants, the relationship is mutually beneficial to both partners, and is vital for the survival of both plant and insect. In fact, yuccas cultivated in the Old World, where yucca moths are absent, will not produce seeds unless they are hand pollinated. Perhaps, if the plant doesn't flower the moth may be missing. BTW, the flower pods may be removed after they open and disperse their seeds... Good luck!