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November 22, 2023

LSU AgCenter's Weekly Message

Pokey, Spikey Plants in Louisiana, Part 1: Yuccas and an Agave

It was just this year that I learned that some yucca plants are indigenous to Louisiana. I suppose I had never thought much about them and just didn’t think they looked like Louisiana natives. They look like they belong in a desert, which our area is not, despite this year’s lack of rainfall. That lesson inspired me to write about yuccas and other Louisiana natives that are a bit prickly.

A handful of the many existing Yucca species are considered native to Louisiana. These include Spanish-bayonet (Yucca aloifolia, AKA aloe yucca), Spanish-dagger (Y. gloriosa, AKA moundlily yucca), Adam’s needle (Y. filamentosa, AKA bear-grass or spoonleaf yucca), and Gulf Coast yucca (Y. louisianensis). Gulf Coast yucca is considered by some to be Y. flaccida (weak-leaf yucca) rather than a separate species.

These yuccas share a number of things in common. They’re evergreen; have long, narrow leaves that come to a point at the tip; and tend to grow on dry, sandy, sunny sites. They produce clusters of white or off-white, bell-shaped flowers on stalks that extend above the leaves. Yucca flowers are often or exclusively pollinated by yucca moths in the insect family Prodoxidae.

Spanish-bayonet and Spanish-dagger both have upright habits, often growing to approximately 4 and 6 feet in height, respectively, although they can get much taller. They have spines on their leaf tips, though those of Spanish-dagger are not as sharp. Spanish-bayonet has very small but sharp teeth (serrations) along its leaf margins, while Spanish-dagger does not. The leaves of Spanish-dagger are a little less rigid than those of Spanish-bayonet.

While Spanish bayonet and Spanish dagger have upright growth habits, the leaves of Adam’s needle and Gulf Coast yucca remain close to the ground. Both can have threads along the leaf margins, although it appears that these occur more consistently on Adam’s needle than Gulf Coast yucca. Leaves of Adam’s needle are stiff, while those of Gulf Coast yucca tend to bend. ‘Color Guard’ is a cultivar of Adam’s needle that has variegated leaves.

The succulent plants in the Agave genus are close relatives of yuccas. Louisiana is at the edge of the American century plant’s (Agave americana) native range, which extends towards the southwest and into Mexico. This plant doesn’t necessarily bloom exactly at the 100-year mark – it’s often much earlier – but the parent plant does die after it flowers. However, it typically produces small plants near its base before it dies. While many yuccas have spines at the tips of the leaves, American century plant has spines along the margins of the leaves, also. The vegetative part of this plant grows to approximately 6 feet tall and wide.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).

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