Flower:

Loose, branching cluster of a few to many stalked flowers at the top of the stem and arising from the upper leaf axils. Flowers are usually white, sometimes pink, less than ¼ inch across with 5 spreading petals each deeply divided into 2 rounded lobes. Flowers open on sunny days.

The calyx is up to 1/3 inch long, initially narrowly oval-elliptic becoming inflated and more bell-shaped in fruit. At the tip are 5 triangular lobes that are frequently tinged dark reddish purple; the outer surface is sticky and has 10 parallel ribs. The underside of the petals may also be reddish purple. Sometimes petals are absent altogether, or very short and hidden inside the calyx tube. The calyx and flowering stalks are hairless except for fine hairs around the edges of the calyx lobes.

Leaves and stems:

Leaves are stalkless, 1 to 2 inches long and may be rough textured to minutely hairy with fine hairs around the leaf edges. Basal and lower stem leaves are generally spatula-shaped. Stem leaves are opposite, toothless, becoming more linear-oblong as they ascend the stem and reduced to bracts in the flower clusters.

Stems are slender, erect, unbranched or few branched, hairless to minutely hairy and typically with dark reddish, sticky patches between the leaf nodes that catch debris and unwary insects.

Fruit:

As the calyx dries, the 10 ribs on the outer surface become more pronounced. Inside is an oval capsule containing tiny dark gray to black seeds.

Notes:

Sleepy Catchfly is a rather variable species, apparently greatly affected by environmental conditions such as moisture, sunlight and nutrients. Flower color, whether petals are absent, size and shape of leaves, whether sticky patches are present on stems, and whether plants are spindly with just one to a few flowers or robust with many flowers are all variable.