Plant of the Week

Trillium ludovicianum range map.
Trillium ludovicianum range map. USDA PLANTS Database.

Trillium ludovicianum.
Trillium ludovicianum. Photo by Charles Allen.

Louisiana Trillium (Trillium ludovicianum)

By Mark Pistrang

All trillium species belong to the Liliaceae (lily) family and are rhizomatous herbs with unbranched stems. Trillium plants produce no true leaves or stems above ground. The “stem” is actually just an extension of the horizontal rhizome and produces tiny, scalelike leaves (cataphylls). The above-ground plant is technically a flowering scape, and the leaf-like structures are actually bracts subtending the flower. Despite their morphological origins, the bracts have external and internal structure similar to that of a leaf, function in photosynthesis, and most authors refer to them as leaves.

Trilliums are generally divided into two major groups: The pedicellate and sessile trilliums. In the pedicillate trilliums, the flower sits upon a pedicel that extends from the whorl of bracts “erect” above the bracts or “nodding” recurved under the bracts. In the sessile trilliums there is no pedicel and the flower appears to arise directly from the bracts.

Louisiana trillium is a sessile trillium that typically flowers from early March through April. Its preferred habitat is mixed pine-beech woods, steep ravine slopes leading to floodplains, and the low flatwoods and floodplains along streams. Lousiana trillium is one of the many trilliums that can be confused with Trillium cuneatum, separated primarily by petal width. Louisiana trillium is only known from Louisiana and Mississippi (possibly Alabama), but it overlaps and intergrades with Trillium cuneatum within the Mississippi portion of its range.

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Schultz’s Milk-vetch (Astragalus molybdenus var. schultziorum).
Schultz’s Milk-vetch (Astragalus molybdenus var. schultziorum)