Lepidium orbiculare is a branching shrub that grows to over 33 cm tall. The young shoots are glabrous, and the leafy branchlets have a diameter of 1–3 mm and are dark purple, transitioning to older stems 3–6 mm in diameter with a purplish hue. The internodes are short, ranging from 1–6 mm, and the nodes are not enlarged. Leaf scars are 3–4 mm wide, lunate, whitish, and nearly flush with a single bundle scar, while leaves are clustered at the stem apex. The leaves are simple and alternate with oblanceolate blades measuring 4.5–7.5 cm in length and 1.9–2.9 cm in width, colored green, and thick chartaceous. The leaf apex is subacute, and the base is cuneate. Initially, the upper surfaces near the midrib are covered with appressed hairs but soon become glabrous, whereas the lower surfaces are glabrous from the start. The margins are low apiculate crenulate, and each half of the blade has 7–9 strongly ascending secondary veins. The petioles are 15–25 mm long, glabrous, slender, and channeled above, without stipules. Flowers appear in a panicle measuring 17 x 10 cm, composed of several minutely puberulous racemes. These bisexual flowers have 5–7 mm long pedicels, a calyx of four sepals 8 mm long, ovate to broadly oblanceolate, with thickened, puberulous central areas and white, membranous broad margins. The corolla consists of four spatulate, white petals that are 0.8 mm long. Six exserted stamens with 1 mm long filaments and subglobose anthers are 0.2 mm in diameter. The superior ovary is orbicular and 0.7 mm long, with a style of 0.2 mm and discoid stigmas of the same diameter. The fruit is a shiny, orbicular capsule 3.5–4 mm in diameter with a reticulate surface and a rounded or slightly emarginate apex. The seeds are orbicular, flat, shining, reddish-brown, and measure 1.3–1.7 mm in diameter, each encircled by a pale membranous wing 0.1–0.2 mm wide. It is found at only two sites near Haupu (peak) in the Haupu Range on the southeastern side of the Kauai.