Solitary herb with a single, thick root (storage organ) ending in an unbranched or moderately branched, short caudex. Each caudex branch ends in 2–3 basal leaves, often with a single, ascending to erect stem with 3–5 leaves and an inflorescence. Stems 2–3 cm in flower stage, extending to 10 cm (or more) in fruit stage. The entire plant is glabrous.
Leaves alternate. Basal leaves erect, up to 5 cm, with a winged petiole up to 4 cm and a blade up to 1.0 × 0.4–0.5 cm, i.e., petiole usually 3–5 times as long as blade. Blade oblong to ovate, obtuse. Petiole and blade dark green or sometimes tinged with purple. Stem leaves similar to basal leaves but gradually smaller and with shorter petioles upwards on the stem, the uppermost nearly sessile.
Inflorescence a raceme with 7–12(14) ebracteate flowers, very short in flowering stage, 8–12 × 6–8 mm, elongating appreciably in fruiting stage to 30–50 mm or more. Pedicels in flowering stage 1–2 mm, elongating slightly in fruiting stage to 2–3(4) mm. Fruiting pedicels and fruits more or less appressed to stem.
Flowers radially symmetric with 4 free sepals and petals, ca. 4.0–4.5 mm in diameter. Sepals 1.8–2.2 × 0.7–1.2 mm, oblong, obtuse to rounded, dark purple with pale purple or pink hyaline margins. Petals 2.3–2.7 × 1.0–1.4 mm, with a short claw and a rounded blade, white. Stamens 5; filaments 1.0–1.5 mm, not much flattened; anthers almost round, 0.5. mm. Gynoecium of two carpels with two rooms separated by a secondary hyaline wall.
Fruit a siliqua, 5–7 × 0.9–1.2 mm, narrowly elongate, narrowing towards the apex and therefore with an acute appearance, dark green or often purple, with 4–6(8) seeds in one row in each room. Style ca. 0.5 mm, slender, cylindrical. Seeds 1.5–2 mm, brown.
Sexual reproduction by seeds; no vegetative reproduction. Adapted to insect pollination but self pollination probably prevails. Seeds ripen regularly.
No special adaptation to seed dispersal and the dispersal is probably very limited.
Eutrema edwardsii can be mistaken for Braya purpurascens, Cardamine bellidifolia, Cochlearia groenlandica, or white-flowered species of Draba. Eutrema differs from Braya in being glabrous and in the fruits appearing acute, whereas Braya is pubescent in most parts and has broadly sausage-shaped fruits; from Cochlearia in being a moderately long-lived perennial with few and narrow basal leaves and in the narrow and appressed fruits, whereas Cochlearia mostly is biennial with numerous basal leaves with broad blades and with short, broad and patent fruits; and from all species of Draba in being glabrous and in the shape of the fruit, narrow, terete, appressed and appearing acute, whereas all white-flowered species of Draba are more or less pubescent and have fruits that are more or less flat, more or less patent, and never appearing acute.
This low-grown species is probably not a strong competitor and is usually growing in heaths and moss mats with a relatively sparse vegetation cover in areas with calcareous soils and other environments with basic soil conditions (such as arctic steppe). It seems to need snow protection and a quite stable water supply.
The presence in the colder parts of Svalbard indicates that the species is not thermophilous. It occurs in the middle and northern arctic tundra zones and the clearly continental to transitional sections. Eutrema has localities scattered throughout the calcareous areas in the fjord districts of Spitsbergen from Sørkapp Land north to Wijdefjorden and Liefdefjorden, with the strongest concentrations at inner Isfjorden and inner Wijdefjorden. There is one locality reported from Edgeøya (Plurdalen) but voucher specimen has not been seen. It is generally absent from the sandstone areas around Longyearbyen and farther west in Isfjorden.
The global range is arctic circumpolar with only a few transgressions into boreal mountains in NE Asia and Beringian North America. All its relatives are found in C and E Asian mountains.
Eutrema edwardsii is overdue for a combined morphological, cytological and molecular investigation in the Arctic. Its relatives in the genus are all Asian, reaching south to the surroundings of Himalaya, and E. edwardsii is the only arctic representative of the genus. It has the same general appearance everywhere but varies significantly in size, the largest plants being found in the Beringian areas. Three ploidy levels are known (tetraploid 2n =28, hexaploid 2n = 42, and octoploid 2n = 56, see Elven et al. 2011) but no chromosome number is known from Svalbard.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/