Soaptree Yucca has Long, slender, green sharp-tipped leaves with strong white margins. White threads also highlight the leaf margins and form a dense crown atop stout branches. During spring, tall, branched stalks form on mature plants to display bell-shaped white flowers high above the foliage. These attractive blooms are NM state flowers. Soap tree Yuccas are found from southern NV, throughout AZ, to southern NM, and into west Texas and are hardy to about -10°F with well-drained soil. These Yuccas quickly develop a tap root, so they resent being moved once established, so pick the perfect spot to plant them and leave them forever.