Oligoneuron riddellii

Native

Wet. Meadows, swamps, fens, wet prairies. Limey soil.

Early August to late September

Yellow ray florets, yellow disk florets

1½′ to 3½′

This is a 1½′ to 3½′ tall, erect, perennial forb with rising on 1 to 10 stems from a well-developed, branching caudex or, sometimes, a creeping rhizome.

The stem is erect, thick, and hairless except for some fine short hairs in the inflorescence.

Basal and lower stem leaves are grass-like, long, narrow, and hairless. They are 4″ to 9½″ long, ⅓″ to ⅔″ wide. They are folded along the midrib, V-shaped in cross section, and often bent backward. They taper to a long, winged leaf stalk. They are usually withering by the time the plant is in flower.

Stem leaves are alternate. Middle and upper stem leaves are attached to the stem without a stalk. They are 2″ to 2¾″ long, ⅓″ to a little less than ½″ wide, becoming gradually smaller as they ascend the stem. They are folded along the midrib and wraps around (sheaths) the stem at the base. They are not dotted with glands.

The stem and side branches terminate in flower clusters which form a flat topped inflorescence of between 30 and 450 flower heads. Each flower head has 7 to 9 yellow ray florets and 6 to 10 yellow disk florets.

Among the flat-topped goldenrods this species is identified by its grass-like, folded leaves.

Grass-leaved goldenrod (Euthamia graminifolia var. graminifolia) has grass-like, unfolded leaves that do not wrap around (sheath) the stem at the base. They have tiny brown to black resinous dots on the surface. Each flower head has 15 to 25 ray florets.

Great Plains flat-topped goldenrod (Euthamia gymnospermoides) has grass-like, unfolded leaves that do not wrap around (sheath) the stem at the base. They have a large number of resinous dots on the surface. The flower clusters have only 10 to 21 flower heads. There are 10 to 14 ray florets in the flower head.