Yucca glauca, an agave, is the hardiest yucca growing from Alberta, Canada all the way to Texas. You will either love or hate this plant depending on your appetite for desert-like plants. I love them for their spiky leaves and fantastic flowers. They are extremely drought tolerant and easy to grow.
The white spikes show up in mid-summer and become the focal point of the garden for several weeks. It is best grown on the side of a hill where they can be seen from various vantage points. The flower spike is a bit shorter than Yucca filamentosa, but it is stiffer and does not need to be staked. The end of the leaves have a needle-sharp spine, so it is a good idea not to plant it right next to a pathway. It likes to be dry, with poor soil. If it is grown in wetter, nutrient-rich soil, the leaves will be less rigid.
The soap-weed yucca is also called narrow-leaf yucca, plains yucca, and bear-grass. It can take a number of years before it is large enough to flower and it may not flower every year. It is only pollinated by the yucca moth which is small, white, and not very striking. I have seeds this year so the moth must live in Ontario even though it is not native here. The relationship with this moth is fascinating and well documented by the USDA Forest Service in this link.
As the plant ages it forms side shoots as well as a trunk up to 60 cm (two feet) tall. The whole clump can become several feet wide over many years. The old lower leaves can be cut off as they age. Newer leaves remain evergreen even in winter.
The roots can be mashed in water to form a liquid soap, and the leaves have been used to weave baskets.
Life Cycle: perennial
Height: 60cm (2 ft), flower spike adds 75 cm (2.5 ft)
Bloom Time: mid-summer
Natural Range: Central North America from Alberta to Texas
Habitat: dry plains and sandy hills
Synonyms: Yucca angustifolia
Cultivation of Yucca glauca
Light: full sun
Soil: lean and sandy
Water: very drought tolerant
USDA Hardiness Zone: 4– 10 (3 with very good drainage)
Propagation: seed, division of root, root cuttings