Arabis holboellii is a tall biennial or short-lived perennial herb in the Mustard family (Brassicaceae), with small white (occasionally purple) flowers and long siliques at maturity. Growing up to 1 m tall from a taproot, plants are typically found in warm, rocky soils, in the subalpine or open sites along riverbanks, slopes and terraces. The stems are usually solitary, hairy at the base and glabrous above. The basal leaves form a tight rosette, are oblanceolate, and are covered with minute stellate hairs. The stem leaves are opposite, clasping and oblong to linear. The perfect flowers are in densely flowered racemes with small (6 - 10 mm long) white to purple petals. The fruits are siliques, a long, narrow seedpod 3-8 cm long and 1-1.5 mm wide. The siliques are decumbent and strongly appressed to the stem, distinguishing this rockcress from others in Alaska which have erect or spreading fruits.
Arabis holboellii is biennial or short lived perennial with diploid and triploid forms, the diploid forms flowering the first year and mostly for only one year (Bocher 1954). It typically flowers in early summer, fruiting shortly after.
Plants are monoecious and have bisexual flowers. The flowers are pollinated by insects, but fertilization is not necessary for seed production. Arabis holboellii can reproduce via apomixis, producing seeds clonally (Sharbel and Mitchell-Olds 2001). Globally, populations consist of diploids, triploids and aneuploids (individuals with irregular chromosome numbers). Diploid plants can be both sexual and apomictic. Triploid and aneuploid populations are strictly apomictic. Seeds are produced in siliques, which split open to allow dispersal via gravity and water.
Puccinia monoica, a rust fungus, produces pseudo-flowers on Arabis holboellii. The fungus is parasitic, preventing Holboell's rockcress from forming flowers and forcing it to turn clusters of leaves into pseudo-flowers which bear the spermatagonia of the fungus (Roy 1993).
The Thompson Indians of British Columbia chewed the leaves for toothaches and the Navajo used it in the Night Chant Ceremony (Moerman 1998).
Holboell's rockcress, in the broad sense, occurs in Greenland and widely across North America with several subspecific varieties. Recently four varieties have been elevated to a species rank (Flora of North America). Boechera retrofracta is the taxon found in Alaska in this new treatment. This species occurs widely in North America and in the eastern interior of the Alaska, but is known from one location in the park, near the Toklat River, on the north side of the Alaska Range.
Holboell's rockcress is found at 330 m elevation on the Toklat River in Denali. Throughout Alaska it is most often found on south-facing or exposed river bluffs, steppes and floodplains in the lowlands and uplands.