Perennial herb up to 10 cm tall; stems and rootstock slender. Radical leaves 7– 20 mm long, simple, densely covered with stellate hairs on petiole, lamina, and margin when young, becoming ± glabrous with age; early radical leaves often simple with few serrations, later leave s pinnatifid or pinnatisect, lobes in 2–4 opposite or subopposite pairs; lamina 4–9 × 1 .5–5 mm; petioles 3–14 × 0 .2–0.5 mm, channelled. Cauline leaves 1– 4, lower leaves similar to radical leaves, uppe r cauline leaves c. 3 × c. 0 .5 mm, linear, often with minute serrations. Inflorescences 4–10 cm long, with 3–10 flowers, peduncle at base c. 0.5 mm diam., racemose, glabrous or with sparse stellate hairs. Pedicels 8–12 × 0 .4–0.5 mm, glabrous. Peduncle, pedicels, and siliques with slight glaucous bloom. Sepals 1 .8–2.4 × 1 .0–1 .1 mm, ascending, oblong to elliptic, with sparse stellate hairs, green with pale margins, subacute. Petals 3 .0–5.0 × 0 .3–1 .0 mm, white, weakly obovate to obovate-spathulate, subacute, claw ± distinct; limb spreading. Stamens 4–6, of unequal lengths; filaments 1 .5–2.5 × c. 0.2 mm, linear; anthers 0 .4–0.7 mm long, yellow. Ovary at anthesis 2 .0–4 .0 × 0 .3–0.5 mm, terete, light brown or green-brown, glabrous; style 0.1–0.2 mm long, green; stigma c. 0.3 mm diam.; ovules 40–62. Siliques 15–25 × 0.7–1.0 mm, terete, often curved, glabrous; valves green in lower part, brown-green or light brown in the upper part. Seeds 0.6–0.9 mm long, short-oblong, pale brown, numerous and in one row in each locule. FL Oct–Nov; FT Oct Dec. Chromosome number 2n = 20 (M. I. Dawson pers. comm.; CHR 510585). Endemic .

Differt ab I. novae-zelandiae habitu exil i parvoque, folius, inflorescentiis, floribusqu e minoribus, etiam ovario tereti.