Members of the agave family, yuccas (Yucca spp.) comprise nearly 40 different species of shrubby perennials from North America and the Caribbean basin. Their sword-like leaves are evergreen and architecturally ornamental. Yuccas are slow-growing plants.
All yucca species produce white flowers that are bell-like and pollinated by moths at night. The upright flower stalks to hold many flowers, collectively called an inflorescence. After the flower drop off, seeds may develop; gardeners should cut off the stalk to keep the plant looking attractive.
Yuccas bloom during the warmest part of the growing season when days are long or shortening heading towards the autumnal equinox. Varying according to each species of yucca, flower typically occurs every year anytime from midsummer to mid fall according to the American Horticultural Society's "A-Z Encyclopedia of Garden Plants."
Not all species of yucca bloom with similar regularity or visual prominence. As these plants are slow-growing, some take considerable time to mature to an age that produces flowers. Once a plant does bloom, expect blooms to return again the subsequent years at the same time of year.