Flower:

Branching clusters at the top of the plant and arising from leaf axils in the upper plant. The flowers are cup shaped, about ½ inch across, the 5 oval to broadly lance shaped petals bright to golden yellow, often orangish-red at the base. In the center are 5 short yellow stamens. The 5-lobed calyx is tinged red around the edges and fringed with hairs.

Leaves and stems:

Leaves are in whorls of 3 or 4, the lowest leaves opposite, 2 to 4 inches long and ½ to 1½ inches wide, toothless, lance to broadly elliptic, on a short stalk. The lower surface is densely softly-hairy. Stems are erect and softly-hairy, starting out mostly unbranched, becoming much branched later.

Notes:

Introduced as a garden ornamental worldwide, it appears to prefer northern temperate regions where it can escape into surrounding native eco-systems. In the slow process of recognizing the ecological threat from the invasive potential of any naturalizing garden species, Garden Loosestrife is being added to invasive species lists in both the northwest and the northeast U.S. It can spread rampantly from vigorous rhizomes and in Washington State it has been observed out-competing the highly invasive Purple Loosestrife (Lythrum salicaria). Garden Loosestrife appears on no list in Minnesota - yet. Our own specimen was photographed in a roadside wetland SE of Grand Rapids back in 2004 may be the only observed rural population in Minnesota to date. While there's undoubtedly more out there, it has yet to hit a population threshold that puts it on the invasive species radar screen here. This is one to pay attention to.