Basaltic Larkspur: Delphinium basalticum - Imperfectly formed version of Delphinium trolliifolium or low elevation form of Delphinium glareosum. Needs further study.
Burke's Larkspur: Delphinium xburkei
Burke's Larkspur, Meadow Larkspur, Twospike Larkspur, Two-spike Larkspur: Delphinium distichum (Synonyms: Delphinium burkei (misapplied), Delphinium strictum, Delphinium strictum var. distichiflorum) - Plants 40-70 cm high. Stems often hollow. Leaves clustered more frequently towards the lower stem and base with th upper leaves noticeably different in appearance to those at the base or lower stem. Inflorescence crowded and the pedicels often less than the calyx spur. Sepals cupped florward, 7-11 mm long.
Olympic Larkspur, Olympic Mountain Larkspur, Rockslide Larkspur: Delphinium glareosum (Synonyms: Delphinium basalticum, Delphinium caprorum, Delphinium glareosum ssp. caprorum, Delphinium glareosum ssp. glareosum, Delphinium glareosum var. caprorum) - Plants 20-30 cm high. Stems hollow. Leaves fleshy and largely basal or on the lower stem. Inflorescenc open, freely branched and often more than half the height of the plant. Lower pedicels several tis longer than the spurs. Roots fibrous, freely branched and firmly attached to the base of the stem.
Duncecap Larkspur, Pale Larkspur, Mountain Larkspur, Sierra Larkspur, Western Larkspur: Delphinium glaucum (Synonyms: Delphinium occidentale, Delphinium occidentale ssp. occidentale, Delphinium scopulorum, Delphinium scopulorum var. glaucum, Delphinium scopulorum ssp. occidentale, Delphinium splendens) -
Thinpetal Larkspur, Thin-petal Larkspur, Upland Larkspur: Delphinium lineapetalum (Synonym: Delphinium nuttallianum var. lineapetalum) - Pale (creamy to pale blue or lavendar) of Delphinium nuttallianum recognized in Washington but not currently in Oregon. Voucher specimen from Rock Creek (Klickitat County, WA)
Cliff Larkspur: Delphinium menziesii ssp. menziesii (Synonyms: Delphinium menziesii, Delphinium menziesii ssp. pyramidale, Delphinium menziesii var. menziesii, Delphinium menziesii var. pyramidale) - Plants 20-100 cm high. Stems somewhat shaggy due to wavy or crinkled hairs. Inflorescence loose and few-flowered. Pedicels typically much longer than the sepals. Sepals widely flared, greater than 12 mm long. Roots one to several, spherical to spindle-shaped, not well branched or fibrous. Stems fairly easily detached from root system.
Two-lobe Larkspur, Upland Larkspur: Delphinium nuttallianum (Synonyms: Delphinium bicolor, Delphinium decorum ssp. tracyi, Delphinium lineapetalum, Delphinium nelsonii, Delphinium nuttallianum var. fulvum, Delphinium nuttallianum var. levicaule, Delphinium nuttallianum var. lineapetalum, Delphinium nuttallianum var. nuttallianum, Delphinium pauciflorum, Delphinium sonnei) - Plants 20-45 cm high. Stems single and not hollow. Lower petals white or pale blue and often heavily blue-penciled and deeply notched at the tip, from 1/4-1/2 the length. Roots fibrous, freely branched and firmly attached to the base of the stem.
Nuttall's Larkspur, Upland Larkspur: Delphinium nuttallii (Synonyms: Delphinium nuttallii ssp. nuttallii, Delphinium oreganum?) - Plants 40-60 cm high. Stems somewhat shaggy due to wavy or crinkled hairs. Racemes compact and many-flowered. Pedicels short, often less than the sepals. Sepals cupped forward, generally less than 12 mm long. Stems fairly easily detached from root system.
Columbian Larkspur, Cow Poison, Cow-poison, Poison Larkspur: Delphinium trolliifolium - Plants 70-150 cm high. Stems often hollow. Leaves well distributed along base and stem, those of the upper stem much like those at the base and lower stem. Blades sharply toothed. Inflorescence loose. The lower pedicels are much longer than the calyx spurs. Sepals flared outwards, 18-25 mm long.