Mark A. Miller
Plant Common Name
This remarkable genus from the Americas comprises around 40 species which are distributed across North and Central America as well as parts of The West Indies. Yuccas are easily identified by their large, dense, distinctive rosettes composed of many sword-shaped leaves. These may be soft and floppy or stiff and wickedly barbed at the tips. Leaf color varies but tends to be in shades of green to pale gray-green. Some yuccas remain stemless and ground-hugging, while others, such as the famous California Joshua Tree, develop tree-like habits.
Tall, branched candles of ivory or white flowers appear at various times in spring or summer. Though open during the day, Yucca blooms can only be pollinated at night by certain moths; specific Yucca species have single moth species that pollinate them, a true instance of coevolution. At night, the yucca flowers emit a unique, soapy fragrance and turn upwards to receive their pollinators. The moths gather balls of sticky Yucca pollen and actively pollinate the flowers. Then the female moths lay their eggs in the flower’s ovaries and plug the ovipositor hole with a ball of sticky pollen. When the larvae hatch, they consume some, but not all, of the developing seeds. Enough seeds remain to fall to the ground and germinate. This is one of the most interesting and well-researched plant/pollinator relationships. The capsule fruits are large, oval, fleshy and turn from green to dry, papery brown.
Select species of yucca have a wide distribution and can be grown in many locations north or south. Yucca flaccida and Yucca glauca are two of the toughest, most cold hardy yucca for northern gardens. A popular garden plant across the whole of the eastern United States is Yucca filamentosa (Adam’s needle), and Yucca gloriosa is a southern favorite. Yucca elata) and Yucca brevifolia (Joshua tree) are outstanding tree-like specimens for desert climates. Many more garden-worthy species exist.
Yucca are easy to grow, and though culture is species specific, most thrive in full sun and well-drained soil with average fertility. Desert species are highly amenable to poor, rocky or sandy soils. In the landscape, Yucca are grown as specimen plants to draw visual focus to specific garden areas. They offer fine-textured foliage along with bold, architectural forms. Plant them along a patio or outdoor room where their night blooms are best enjoyed.
Yuccas have long been used by Native Americans for soap making, food, and fiber. The roots of some species are high in saponins, which can be mixed with fats to make basic soap. The stems, flowers, and seeds of most, but not all, Yucca are edible and may be eaten cooked or raw. And the soft, strong, pliable Yucca leaf fibers are useful for making everything from ropes to woven blankets and sandals.