Flower:

Flowers are long stalked, arising from leaf axils, 1 flower per axil. Flowers are ½-inch across, star-shaped with 5 yellow petals, sometimes with a few red streaks on the surface and/or red tinged around the edges. Petals are red at the base, forming a ring around a center column of red-tipped yellow stamens, that are fused at the base and which surround the style.

Leaves and stems:

Leaves are generously spaced along the stem, whorled in groups of 3 to 7 but typically 4 or 5. Leaves are oval to lance elliptic, 1¼ to 4½ inches long and 1/3 to 1½ inches wide, pointed at the tip, tapering or rounded at the base, toothless, with little to no stalk. Leaf edges and underside may be covered in scattered fine hairs. The upper surface is covered in small darkened pits. Stems are erect, usually unbranched, smooth to finely hairy, especially at the leaf nodes.

Notes:

The star-shaped flowers and pitted leaves distinguish Whorled Loosestrife from other yellow loosestrifes that have long-stalked flowers in the axils, and its typically (in Minnesota) drier forest habitat further separates it from the rest. According to the DNR, Lysimachia quadrifolia was unknown in Minnesota until 1980 when a plant survey discovered it at St. Croix State Park. Further surveys uncovered several more populations in the park but in 2009 the plant was still unknown outside of Pine county and had been listed as a Special Concern species in 1996. However, working as a Master Naturalist volunteer for the DNR, Katy Chayka discovered and photographed a specimen in 2007 at Wild River State Park in Chisago County, As identifying rare plant species had not been part of her Master Naturalist training, a connection wasn't made until 2011 when she notified Natural Heritage Program staff with her discovery. A follow-up survey of the area in the spring of 2012 revealed a substantial new population in the immediate vicinity of the specimen she photographed back in 2007. A more thorough survey of the St. Croix River valley may yet reveal additional populations.