shy wallflower

not listed

N5? - Secure

SNR - Unranked

not listed

Shy wallflower is a 12″ to 32″ tall, erect, biennial or short-lived perennial forb that rises on 1 or a few stems from a thickened caudex.

The stems are erect, hairless, grayish-green, and usually unbranched below the inflorescence. They are densely covered with hairs that lay flat and have two branches that extend in opposite directions, appearing as a straight line.

Basal leaves are linear to narrowly inversely lance-shaped, ⅝″ to 2⅜″ long, and 1 ⁄16″ to 5 ⁄16″ wide. They are not lobed. The leaf blade tapers gradually to a narrow point at the base and tapers to a point at the tip with straight sides along the tip. The upper surface is covered with a mix of 2-branched and 3-branched hairs. The margins are usually untoothed, sometimes toothed with shallow, broad teeth.

Stem leaves are alternate, mostly erect or ascending, rarely more than 3 ⁄16″ wide, and otherwise similar to basal leaves. Lower stem leaves taper at the base to short leaf stalks. Upper stem leaves taper at the base to the stem. They do not partially or completely surround the stem at the base.

The inflorescence is a densely-flowered, unbranched, elongated cluster (raceme) at the end of the stem. The flowers are not subtended by bracts. They are held stiffly erect on stout, ascending, ⅛″ to ⅜″ long stalks.

Each flower is about ½″ to ¾″ wide. There are 4 sepals, 4 petals, and 6 stamens. The sepals are green, erect, linear to narrowly oblong, and ⅛″ to ¼″ long. They are densely covered with star-shaped hairs. The lateral pair of sepals are slightly shaped like a pouch or sack at the base. The petals are light yellow to yellow and are not conspicuously dark-veined. They are inversely lance-shaped, ¼″ to ⅜″ long. They are unlobed, rounded at the tip, and abruptly narrowed to a 3 ⁄16″ to ¼″ long stalk-like base (claw). There are 6 stamens, 2 short, outer stamens and 4 longer, 3 ⁄16″ to ¼″ long, inner stamens. There is one 1 ⁄32″ to 1 ⁄16″ long style with a 2-lobed stigma.

The fruits are narrow pods held erect or ascending on 3 ⁄16″ to ½″ long stalks. The fruit stalk (pedicel) is noticeably narrower than the fruit. Each fruit is narrowly linear, 13 ⁄16″ to 2″ long, and 1 ⁄32″ to 1 ⁄16″ wide. It is round or slightly 4-angled in cross section. It is not striped and is not constricted between the seeds. It is covered with 2- to 4-branched hairs. When mature the pod splits and the two sides fall away leaving the transparent interior partition attached to the plant.

12″ to 32″

Light yellow to yellow

Dry. Prairies, woodland openings, railroads, roadsides.

May to August

This and other mustards (family Brassicaceae) produce chemical compounds when cells are damaged that are toxic to most animals, fungi, and bacteria.

Sources

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

Native

Plant

Infructescence