Flower:

1 to 5 stalked flowers in a branching cluster at the tip of the stem. Flowers are ¼ to 3/8 inch across, 5 oblong-elliptic white petals and 10 white-tipped stamens surrounding a greenish ovary with 3 spreading styles in the center. The stamen tips may turn black with age. Behind the flower are 5 light green sepals that have pointed tips and extend to about 1/3 the length of the petals. At the base of a flower stalk is a pair of tiny scale-like bracts.

Leaves and stem:

Leaves are 1 to 1½ inches long and 1/8 to 1/3 inch wide, oblong to broadly elliptic, toothless, minutely hairy around the edges and midvein on the underside, blunt or rounded at the tip, and stalkless. Attachment is opposite with leaf pairs at right angles to the pair above and below. Stems are very slender and delicate, typically branched, covered in very short hairs, and mostly prostrate but rising at the tip (decumbent), sometimes ascending.

Fruit:

Fruit is a nearly round capsule, about 1/8 inch long, containing 1 to a few tiny, black seeds, though not all flowers produce fruit.

Notes:

Blunt-leaf Sandwort seems to spread primarily vegetatively through rhizomes, often forming a dense tangle of plants. I was steward for this species for a few years at Wild River State Park and only collected about 4 seeds between the two known sites in all that time. The seed capsules rarely developed fruit and I observed the same at two locations in Ramsey County as well. A very similar species is the rare Large-leaved Sandwort (Moehringia macrophylla), which (as its name suggests) has larger leaves up to 2 inches long, sepals at least half as long as the petals, and is a more erect plant.