Lupinus pilosior, commonly known as the woolly lupine, is a species of flowering plant in the family Fabaceae. It is endemic to peninsular Florida in the southeastern United States, where it occurs in dry, sandy habitats such as longleaf pine sandhills.
The species was described in 2024 as part of a taxonomic revision of the unifoliolate Lupinus species complex, which had previously been broadly treated under Lupinus diffusus.
Lupinus pilosior is a perennial herb with a decumbent to mat-forming growth habit, with stems spreading along the ground. The plant is notable for its dense, spreading villous indumentum composed of long, whitish hairs that largely obscure the surface of the leaves.
Leaves are unifoliolate, a defining characteristic of the group, and are borne on relatively short petioles typically 3âÂÂ4 cm in length. The leaf blades are ovate to elliptic and thickly covered in long hairs.
The inflorescences bear typical lupine flowers with a banner petal that may display a contrasting eyespot. Fruits are legumes approximately 3.5âÂÂ4.5 cm long and 10âÂÂ12 mm wide, larger than those of several related species.
Lupinus pilosior was described by Edwin L. Bridges and Steven L. Orzell in 2024 as part of a comprehensive revision of the unifoliolate Lupinus species of Florida.
Prior to this revision, members of this group were often included within a broadly defined Lupinus diffusus. The revision recognized multiple distinct species based on consistent differences in morphology, ecology, and geographic distribution.
Lupinus pilosior belongs to a clade of closely related species endemic to peninsular Florida, often referred to as the unifoliolate Lupinus species complex.
The species is endemic to peninsular Florida, where it occurs primarily west of the Lake Wales Ridge.
It inhabits xeric upland environments, especially longleaf pine sandhills and dry sandy ridges. These habitats are typically fire-maintained and characterized by well-drained, nutrient-poor soils.
Populations are known from several counties including Pasco, Collier, DeSoto, Manatee, Sarasota, and Hardee.
Lupinus pilosior flowers primarily from March to April.
Lupinus pilosior is part of the unifoliolate Lupinus species complex of peninsular Florida, a group of closely related taxa formerly included within a broad concept of Lupinus diffusus but now recognized as distinct species based on morphology, ecology, and geography.
Species within this complex are distinguished primarily by growth habit (erect vs. decumbent or mat-forming), indumentum (type and orientation of pubescence), leaf proportions, floral characters (especially the banner eyespot), and fruit size.
Lupinus pilosior is characterized by a decumbent to mat-forming habit, stems spreading along the ground, and a dense, spreading villous indumentum of long hairs that largely obscures the leaf surface. It typically has relatively short petioles (about 3âÂÂ4 cm long) and comparatively large legumes (approximately 3.5âÂÂ4.5 cm long and 10âÂÂ12 mm wide).
It differs from other members of the complex as follows:
These differences reflect diversification within fire-maintained, xeric sandy habitats of Florida, with Lupinus pilosior representing a lineage distinguished by its mat-forming habit, strongly villous indumentum, and relatively large fruit size.