Many-lobed Giant Desert Parsley
 (Carrot-leaf biscuitroot) 

Lomatium dissectum
(Nutt.) Mathias & Const. var. 
multifidum
(Nutt.) Mathias & Const

Collected along the trail toward Weippe Prairie northeast of Kamiah in Clearwater Co., Idaho, on 10 Jun 1806. (Source)

The plant grows as much as four feet tall with a tuber-like taproot..  The leaves mostly basil, are large and fern-like, divided into many small segments.  It is known for inflorescence consisting of one to several umbrella-like flower clusters called umbels. The multiple umbels develop on a long, leafless stalk, with flowers that vary in color from deep purple, nearly black to pale yellow.  The white anthers contrast sharply with the petals of the purple flowered form. The individual flowers are small, with five petals, five stamens, and no sepals. The leaves, mostly basal, are large and fern-like. It flowers from April to July. The inferior ovary matures into a dry, two seeded fruit.  It inhabits the the sagebrush steppe. It most frequently grows in rocky habitats, particularly on talus slopes.

Food Uses  
The leaves have an odor similar to common parsley.  The leaves and roots are both edible.  It is used as a meat flavor, and in stews or salads. The greens may be eaten in the spring but become tough and fibrous later in the season. Tea can be made from the leaves, stems and flowers. The stringy roots of all species are edible raw or they may be peeled and the inside dried, then ground into flour. The tiny seeds, though tedious to collect, are edible raw or roasted and can be dried

Medicinal Uses
The roots of the fern-leaved desert parsley were used to make a medicinal tea that was considered a general panacea by many native peoples.  It was used for treating coughs, colds, sore throats, hay fever, bronchitis, flu, pneumonia, and tuberculosis.  Is is used to treat bacterial and viral respiratory infections and to help bring phlegm up from the lungs and bronchia.