Flower:

Nodding yellow flowers ¾ to 1 inch across on slender stalks ¾ to 1½ inches long, arising from leaf axils in the upper stem and branches, typically 1 flower per axil, rarely more. The 5 petals are nearly round, often with ragged or fringed edges, with a sharp, narrow point at the tip and 5 lance shaped sepals at the back that are about ¾ as long as the petals. The 5 stamens have crescent shaped tips that are yellow to light reddish brown and surround a single, slender style in the center. The center is often ringed a light rusty red but not always.

Leaves and stems:

Leaves are opposite, sometimes whorled in 2 or 3 pairs in the upper plant, generally lance to elliptic, 1½ to 3¾ inches long and ½ to ¾ inch wide, gently tapered to a dull tip, rounded to wedge-shaped at the base, on a short (sometimes very short) stalk. The underside is only slightly lighter green than the upper surface.

The lower leaf stalk is edged in short stiff hairs, which are densest at the stem between the leaf pairs. Stem and branches are otherwise hairless, branches numerous and typically longer than the subtending leaf. Early plants are more tightly columnar with flowers along entire stem but as branches develop and extend beyond the leaves, the plant takes on a more open, panicle like form. In favorable conditions colonies can form via its thickened rhizomes.

Notes:

Lowland Yellow Loosestrife is most common in east central and scattered in western Minnesota and can be easily confused with Fringed Loosestrife (Lysimachia ciliata), which is more prevalent and widespread throughout the state. The most distinguishing characteristics of L. hybrida are its narrower leaves that have fewer hairs, which are more concentrated towards the stem attachment, and by its more open branch habit. The whorled leaves may cause it to be confused with Whorled Loosestrife (L. quadrifolia), which has star-shaped flowers and broader leaves whorled along the entire stem, not just near the top. Sometimes known as L. lanceolata var. hybrida, Lowland Yellow Loosestrife also closely resembles Lance-leaved Loosestrife (L lanceolata), which has leaves paler on the underside than the upper surface. L. lanceolata is not uncommon in Wisconsin but has not been recorded in Minnesota, though it may well be present here, most likely in the southeast counties.