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Plant Highlight: Yucca treculeana

April 2006

At the Ruth Bancroft Garden, we have about a dozen species of yuccas, both large and small. Their showy plumes of white or cream flowers are a prominent feature of the garden in spring, although some species do flower at other times of the year. Normally, the first species to come into flower in the garden is Yucca treculeana, a large-growing species from south Texas and northeast Mexico. Its large clusters of flowers, looking from a distance like giant sticks of cotton candy, put on a great show each April. Some kinds of yuccas have flowers loosely spaced along the stalk, but Y. treculeana has many vertical-growing floral branches packed into a dense panicle of hundreds of flowers.

The natural pollinators of yuccas are a group of moths whose occurrence closely matches the distribution of their host plants. After pollination, some species develop capsules which split open as they dry, spilling the black seeds. Others have elongated fleshy fruits, with the seeds embedded in pulp. Yucca treculeana is one of the latter type, but unfortunately our garden is located outside of the natural range of yuccas and their associated moths, and as a result the flowers on our plants do not get pollinated. This means that seed pods do not develop on our plants.

We have two forms of the species planted in the garden. Single-stemmed plants are known in nature, but both of the forms at RBG are clump-forming. One is more robust, with sword-like leaves of 4 feet or longer (about 1¼ meter) and reaching a height of almost 20 feet (6 meters). The other is only slightly less imposing, with leaves a little over 2 feet (.6 m) and a height of 12 feet (3.7 m). Some yuccas have leaf edges that fray, with curling fibers (filifers) decoratively arrayed along the margins. Although there are forms of Y. treculeana which display this character to some extent, our plants do not. If one has the space for it, this yucca is very worthwhile for its dramatic form, drought tolerance, and spectacular floral display. It can take winter temperatures down to at least 10º F (-7º C).