Plant of the Week

Trillium catesbaei range map.
Trillium catesbaei range map. USDA PLANTS Database.

Trillium catesbaei.
Catesby’s trillium (Trillium catesbaei). Photo by Mark Pistrang.

Catesby’s Trillium (Trillium catesbaei)

By Mark Pistrang

Based upon recent genetic research trillium species now belong to the family Trilliaceae. Historically trilliums have been placed in the lily family, Liliaceae. Trilliums 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 small, scale-like leaves called cataphylls. These highly modified leaves surround the flowering scape (the above ground plant) as it pushes up through soil in early spring. The leaf-like structures are technically 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 divided into two major groups: The pedicellate and sessile trilliums. In the pedicellate trilliums, the flower sits upon a pedicel (stalk) that extends from the whorl of bracts. These trillium flowers are either “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.

Catesby’s trillium falls within the pedicellate group. This beautiful spring wildflower’s flower is on a recurved pedicel that curls back under the leaves often obscuring it from view. Flowers are typically seen from late March through June. It is distinguished by its nodding white, pink, or rose colored flowers with egg-yolk yellow anthers and its widely spaced leaves that are rolled inwardly along the length of the leaf. This unusual leaf morphology allows the flower to be more readily observed. Catesby’s trillium tends to occur in drier habitats and is typically found on acid soils, in open dry or rich mesic woods, within laurel and rhododendron thickets. Catesby’s trillium is found in Alabama, Georgia, North Carolina, South Carolina, and Tennessee.

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