Soaptree Yucca

Yucca elata

soaptree yucca at Academy Village

About the Plant

Soaptree yucca is native to southern Arizona and New Mexico, one of the most common yucca in the Tucson area. Though initially a low plant, mature specimens can reach to 10-15 feet and have multiple stems. This plant does not flower every year. When it does, the flower stalk reaches 3-7 feet with all the large creamy-white flowers held well above the foliage.

Grow soaptree yucca in full sun and well-drained soil. New plants should be watered in summer until well established but avoid overwatering, especially in winter. Resist the urge to "improve" their appearance by pulling off dead leaves on the lower trunk. Those leaves provide protection from sunburn, cold, and insect infestation. This yucca is quite cold tolerant, to -10°F.

Distinguish soaptree yucca from agave and other yucca by its thin, flat leaves, absence of spines on the edges of the leaves, and by its white leaf edges that often shred and curl.

Notes:

  • This yucca was widely used by native peoples. See the Weekly Plant article for more details.
  • Soaptree yucca is an Arizona Protected Plant.

Wildlife value: The flowers are pollinated exclusively by yucca moths.

More Information

Weekly Plant on soaptree yucca

Horticultural information from ASU

Map of distribution in US

Technical botanical description from SEINet

In books:

Native PLants for Southwestern Landscapes by Judy Mielke, page 276

Agaves, Yuccas, and Related Plants by Mary & Gary Irish, page 241

ID Characteristics

This plant is in the Asparagaceae - the asparagus family.
Soaptree yucca is a large plant that typically grows to 10-15 feet. As a young plant the leaves form a dense radial head. Eventually a trunk begins to grow, 6-12 inches wide. A mature plant can have as many as 10  trunks, some branching near the top.
The leaves are thin and flexible with a sharp tip but otherwise unarmed. They are 2-3 feet long but less than 1/2 inch wide. The leaf edges are white, composed of compressed fibers that eventually shred and curl, especially at the base of the leaves.  Older leaves brown and hang down, forming a natural, protective thatch.
Soaptree yucca does not flower every year but it does flower often. In late spring, late April into May, a tall flower stalk grows from the center a leaf cluster. Branches near the top of the stalk hold many pendant, creamy-white, bell shaped flowers (some flowers may be tinged with pink or pale green). Sometimes this cluster is so heavy that tall plants will be bent over by its weight.
About 2 inches long, these flowers have parts in 3s, a structure common to monocotyledonous plants. There are 3 sepals and 3 petals (so similar they are usually grouped together as 6 tepals) forming the bell. Inside the bell are 6 stamens and a single pistol with 3 lobes.
If the flower is pollinated by a yucca moth, a 3-part capsule forms. When the black, flat seeds are mature, the capsule splits open.