four-flowered yellow loosestrife

not listed

N5? - Secure

SNR - Unranked

not listed

FACW - Facultative wetland

OBL - Obligate wetland

OBL - Obligate wetland

Four-flowered yellow loosestrife is a 8″ to 27″ tall, erect, perennial forb that rises from a slender, horizontal, creeping, underground stem (rhizome). Rosettes of basal leaves can sometimes be found near the base of the plant rising from the parent rhizome.

The stems are slender, erect or strongly ascending, and hairless. They may appear unbranched or have short branches above the middle. However, the lower nodes usually have very short branches appearing as a cluster of leaves in the leaf axils.

Basal leaves are egg-shaped to elliptic, are shorter than stem leaves, and are on long leaf stalks. They are usually absent by flowering time.

Stem leaves are opposite but sometimes appear whorled due to the leaves in the leaf axils. They are stalkless or nearly stalkless. The leaf blades are linear to very narrowly lance-shaped, 1¼″ to 3½″ long, and 1 ⁄16″ to ¼″ wide. They taper to a sharp point at the tip and are angled or tapered at the base. The upper surface is green to dark green, shiny, and hairless. The lower surface is pale green and hairless. The midvein is prominent and there are no evident secondary veins. The leaf surfaces are not dotted or pitted (punctate). The margins are untoothed, curled under, and may have a fringe of a few long hairs near the base.

The inflorescence is a single flower or whorl of flowers rising from middle and upper leaf axils. Each flower nods at the end of a hairless, ⅝″ to 1⅜″ long stalk. The arrangement often appears as a whorl of four flowers, each one pointing in a different direction and nodding at the end of a slender stalk.

Each flower is ½″ to 1″ in diameter. There are 5 sepals, 5 petals, 5 stamens and a single style. The sepals are united at the base into a very short tube (calyx) then separated at the tip into 5 widely spreading, narrowly lance-shaped, ⅛″ to ¼″ long lobes. They are yellow tinged with green and have 3 to 5 parallel, often reddish-brown veins. They are hairless, not gland-dotted, and not punctate. The petals are yellow, widely spreading, more or less round, and ¼″ to ⅜″ in diameter. They are reddish at the base. They taper abruptly to a point at the tip. The margins are mostly smooth but may be irregularly toothed, appearing gnawed (erose), near the tip. The stamens are free, not fused into a tube. They have yellow reddish and hairy, 1 ⁄16″ to ⅛″ long filaments. The style is ⅛″ to 3 ⁄16″ long.

The fruit is a hairless, shiny, spherical to broadly egg-shaped, ⅛″ to 3 ⁄16″ in diameter capsule. The spreading lobes of the calyx persist when in fruit. The style also persists as a long sharp spine at the tip. The capsule contains up to 20 or more seeds and ripens in the fall.

8″ to 27″

Yellow

Fringed loosestrife (Lysimachia ciliata) is a larger, more robust plant. The leaves are broad, up to 2⅜″ wide, and have a fringe of hairs along the margins.

Whorled loosestrife (Lysimachia quadrifolia) leaves appear in whorls of mostly 4. The leaf blades are broad, elliptic, up to 1⅜″ or more wide.

Moist to wet. Prairies, meadows, edges of ponds and marshes, calcareous fens, bogs, swamps, roadside ditches. In lime-rich soil.

July to August

Sources

2, 3, 4, 5, 7, 28, 29, 30.

Native

Common

Inflorescence

Flower

Leaves