Blackish Oxytrope – Oxytropis nigrescens

Alaska Wildflowers | Purple

The purple-flowered blackish oxytrope (Oxytropis nigrescens)

Blackish Oxytrope

Oxytropis nigrescens

Common Names

blackish crazyweed
blackish oxytrope
purple oxytrope




O. nigrescens var. lonchopoda
O. nigrescens var. nigrescens
O. nigrescens var. uniflora

Genus: Oxytropis (locoweed, crazyweed)
Family: Fabaceae (peas, legumes)
Order: Fabales
Full Classification

Duration – Growth Habit

Perennial – Forb/herb

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Identification and Information

Blackish oxytrope is a 1-5 cm tall perennial herb that grows from a taproot. It has extensively branched horizontal stems that form a cushion. The leaves are compound, greyish-green, distributed along aerial stems, and are covered in dense white or grey hairs. The leaf blades are 50-80 mm long and divided into 5-9 small (3-4.5mm long), oblong or ovate leaflets with curled margins and dense grey hairs.

The flowering stems are also hairy, but do not have leaves. The flowers are solitary or in an inflorescence of two flowers per stem. There are often many flowers on a single cushion. The flowers are bilaterally symmetric with 5 fused 8-9 mm wide sepals. The calyx is 5-lobed, tubular, and covered in dense black (sometimes white) hairs. It has 5 purple or blue petals often with white veins, often white near the base of the petal. Four petals are unlobed or slightly lobed and the fifth forms a helmet that is also either unlobed or slightly lobed. Each flower has 10 stamens and a superior ovary with 1 carpel. The fruit is a black, cylindrical legume.

Note: There is not a wealth of information on blackish oxytrope and its subspecies. The only detailed scientific description that I could find was of the subspecies O. nigrescens var. uniflora (synonym O. arctobia) in the Flora of the Canadian Arctic Archipelago. This source notes that the Oxytropis nigrescens aggregate might be composed of 8-9 very closely related species, or that the North American aggregate is “one variable species with ‘varieties'”. The varieties might be regional. All other descriptions were simple guidebook-type descriptions that seemed to describe this variation without much detail, although I found no information on the differences between the varieties. I use the Flora of the Canadian Arctic Archipelago in this description as nothing stood out as inconsistent from my own observations of the plants in Alaska.


For information only (typically historical) – I take no responsibility for adverse effects from the use of any plant.

Unspecified use as a food, typically the roots. Note that several other species of Oxytropis are reported as toxic.

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Distribution and Habitat

Oxytropis nigrescens is native to Alaska, northern Canada, British Columbia, and Siberia. It grows in gravelly, often in tundra or alpine areas in well-drained soil. It is less frequently seen on gravel bars in river or stream beds.


RankScientific Name (Common Name)
KingdomPlantae (plantes, Planta, Vegetal, plants)
   SubkingdomViridiplantae (green plants)
      InfrakingdomStreptophyta (land plants)
            DivisionTracheophyta (vascular plants, tracheophytes)
               SubdivisionSpermatophytina (spermatophytes, seed plants, phanérogames)
                           FamilyFabaceae (peas, legumes)
                              GenusOxytropis DC. (locoweed, crazyweed)
                                 SpeciesOxytropis nigrescens (Pall.) Fisch. ex DC. (blackish oxytrope)
 Direct Children:
                                    VarietyO. nigrescens var. lonchopoda
                                    VarietyO. nigrescens var. nigrescens
                                    VarietyO. nigrescens var. uniflora (one-flowered blackish locoweed, oneflower blackish locoweed)

References and Further Reading


Field Guide to Alaskan Wildflowers, Pratt, Verna E. pg 10

Classification and Taxonomy

O. nigrescens (Pall.) Fisch. ex DC. Taxonomic Serial No.: 26158, ITIS Database

O. nigrescens (Pall.) Fisch. ex DC., USDA Database


Fabaceae O. nigrescens (Pallas) Fisch. ex DC., Native American Ethnobotany Database

Map and Distribution

O. nigrescens (Pall.) Fisch. ex DC. Published in: Prodr. 2: 278 (1825), GBIF Database

O. nigrescens Blackish Crazyweed, NatureServe Explorer

Description and Information

O. arctobia Bunge, Flora of the Canadian Arctic Archipelago

Blackish Oxytrope • Blackish Crazyweed, Circle District Historical Society

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