Flower:

Stalked flowers, single or in small clusters, at the tip of branching stems and arising from leaf axils near the top of the plant. Individual flowers are ¾ to 1¼ inch across and have 3 petals, the upper 2 petals are round and bright blue, the lower petal much smaller, white and notched into 3 rounded lobes. In the center are 3 small, yellow-tipped, sterile stamens and a 4th stamen with a larger, butterfly-shaped yellow tip. Below are a style and 2 fertile stamens; all 3 are long, curving and blue.

Behind the flower is a folded, leafy bract (spathe) that is up to 1½ inches long, half heart-shaped in outline, and typically covered in short, stiff hairs. The spathe is fused along the bottom third (or more), with only a slit open at the top where the flower emerges. Each flower lasts for a single day, hence the common name.

Leaves and stems:

Leaves are 2 to 6 inches long, up to 1¼ inch wide, lance-linear with a long taper to the pointed tip, a rounded base, stalkless or nearly so, toothless, hairless or with minute stiff hairs, and widely spaced on the stem. Edges are often reddish.

The leaf base extends to form a sheath ½ to 1 inch long, surrounding the stem, with a few long hairs around the tip edge, short hairs along the front edges and a scattered stiff hairs on the surface. The tip of the sheath often has a pair of small, rounded lobes (auricles) that flare out. Stems are erect to ascending, often branched, usually rough, sometimes smooth.

Fruit:

Fruit is a 2 or 3-sectioned capsule, each section containing 2 brown seeds.

Notes:

The only known location for Slender Dayflower in Minnesota is in a sand prairie in Wabasha County. According to the DNR, extensive targeted searches have been performed by the MN County Biological Survey without locating any additional populations. Due to the species' rarity as well as the rarity of potential habitat, it was listed as State Endangered in 2013. A similar species is the non-native Asiatic Dayflower (Commelina communis), which is an annual, has a hairless spathe open at the top all the way to the base, stems that are often prostrate and root at the nodes, lacks auricles on the sheaths, and the yellow stamens typically have a maroon spot in the center of the tip.