Tufted loosestrife, one of several “yellow loosestrifes”, is a native perennial that grows in swamps, at the edge of bogs and in wet prairies, where it’s usually partly shaded by taller vegetation.
Although it’s not a true bog species, it has a low tolerance for calcium and so is usually found on peaty soil. It spreads by seed and by long rhizomes.
Origin of the name: Lysimachia, lysis, Gr., to loosen or release; mache, Gr., a struggle; refers to the practice of putting the flowers under the yoke of oxen to repel insects; thyrsiflora, thyrsos,
Gr., thyrse, refers to the pyramid-like arrangement of the individual flowers.
Range: Circumboreal, in N. Amer. south to NJ, MO, CA
WI Range: Statewide; more common north and east
Common associates: Bluejoint grass, horsetails, marsh fern, poison sumac
Wetland Indicator Status: OBL
Coefficient of Conservatism: C = 6 (MI); C = 9 (S&W)
Plants are erect, unbranched, and less than 0.7 m
tall. The leaves are opposite, up to 12 cm long, undivided, with a pointed tip and tapered at the base.
Pits or dots are visible on the leaves with a hand lens. The flower clusters form in the axils of the leaves, but only the leaves in the middle of the stem.
Dense spike-like flower clusters bloom in
June on stalks, up to 4 cm long. Each tiny flower has six yellow petals with black or purple spots, also only visible with a lens.
Like all the species in the Primrose Family, Lysimachia petals are joined together and each stamen is fused to the middle of a petal. The Primulaceae are the “true primroses”, not to be confused with the Onagraceae or the “evening-primroses”. Purple loosestrife (Lythrum salicaria)
is in yet another family, Lythraceae, and not at all related to the yellow loosestrifes.