Hedysarum boreale ssp. mackenziei is a member of the pea family (Fabaceae) with many large pink flowers, which grows on open gravel bars in early successional habitats. Some years, you can see large areas of it flowering along the Thorofare River gravel bar below Eielson Visitor Center. Hedysarum boreale ssp. mackenziei is a tall (10-30 cm) perennial forb arising from a branched caudex and large woody taproot. Leaves are alternate, pinnately compound with 7-15 leaflets and no obvious lateral veins. Leaflets are ovate to elliptic. The inflorescence is a raceme, 2-8 cm long, of 5-15 large pink flowers. Flowers have the typical bilateral symmetry of the pea family, petals 2.5-3 cm. Fruit is a dry loment (constricted peapod) with 3-6 segments, the joints of the pod are winged—in contrast to its close relative Hedysarum alpinum which does not have wing-margined joints. Hedysarum alpinum looks similar, and can be distinguished by the presence of a visible vein on the underside of leaflets, and the aforementioned lack of wing-margined joints on the pod.
This species is a deciduous perennial that flowers mid-summer.
Hedysarum boreale ssp. mackenziei is monoecious with bisexual flowers. Flowers observed in Fairbanks, Alaska were predominately visited by bumblebees (McGuire 1993). Seeds are likely water and gravity dispersed.
Hedysarum boreale ssp. mackenziei is endemic to North America, where it has a boreal-montane distribution ranging from Alaska east to Baffin Island and from British Columbia east to Quebec, and south to Washington and Oregon. In Alaska, this species occurs primarily in interior and eastern Alaska, but extends farther west in the Brooks Range and Arctic slope. In Denali, this species occurs on the major glacial rivers flowing out of the Alaska Range to the north.
Hedysarum boreale ssp. mackenziei is primarily a low-mid elevation species, occurring from 155 m to 1033 m, with an average plot elevation of 691 m. It primarily grows on flat or low angled sites with an average plot slope of 3 degrees.