Contorted-pod Evening-primrose, Slender Evening-primrose, Twisted Evening-primrose: Camissonia contorta (Synonyms: Oenothera contorta, Oenothera contorta var. contorta) - Plants with stems present. Sepals adhere by their tips in pairs as the flower opens. Flowers yellow. Fruits sessile, linear, straight or coiled.
Delicate Evening-primrose, Great Basin Suncup, Lewis River Suncup: Camissonia parvula (Synonyms: Oenothera contorta var. flexuosa, Oenothera parvula, Sphaerostigma flexuosum, Sphaerostigma parvulum) - Plants with stems present. Basal leaves absent. Stem leaves linear with entire margins. Herbage of leaves and sepals either glabrous or with sparse, short appressed haris. Flowers yellow.
Little Wiry Suncup, Soft Evening Primrose: Camissonia pusilla (Synonyms: Oenothera contorta, Oenothera contorta var. flexuosa) - Plants with stems present. Basal & stem leaves linear with sawtoothed margins. Foliage and sepals with spreading hairs. Sepals all separating as the flowers open. Flowers yellow.
Beach Evening-primrose: Camissoniopsis cheiranthifolia ssp. cheiranthifolia (Synonyms: Camissonia cheiranthifolia ssp. cheiranthifolia, Oenothera cheiranthifolia, Oenothera cheiranthifolia var. cheiranthifolia) - A species of the southern Oregon coast, this evidently was collected at a peninsula jutting into the Columbia River near Hanford.
Browneyes, Club-fruited Evening-primrose, Crossflower Evening-primrose: Chylismia claviformis ssp. cruciformis (Synonyms: Camissonia claviformis ssp. cruciformis, Camissonia claviformis var. cruciformis, Oenothera claviformis var. cruciformis) - Plants with stems present. The leaves are mostly basal. Petals yellow, often with reddish spots near the base of the petals, longer than 4 mm. Fruits on pedicels at least 5 mm long. The pedicels are never twisted or coiled.
Browneyes, Club-fruited Evening-primrose: Chylismia claviformis ssp. integrior (Synonyms: Camissonia clavaeformis ssp. integrior, Camissonia claviformis ssp. integrior, Camissonia claviformis var. purpurascens, Oenothera claviformis var. purpurascens) - Plants with stems present. The leaves are mostly basal. Petals creamy white, often with reddish spots near the base of the petals, longer than 4 mm. Fruits on pedicels at least 5 mm long. The pedicels are never twisted or coiled.
Naked-stemmed Evening-primrose: Chylismia scapoidea ssp. brachycarpa (Synonyms: Camissonia scapoidea ssp. brachycarpa, Oenothera scapoidea, Oenothera scapoidea ssp. brachycarpa, Oenothera scapoidea var. seorsa) - Plants with stems present. The leaves are mostly basal. Petals yellow, less than 4 mm long.
Naked-stemmed Evening-primrose, Paiute Suncup: Chylismia scapoidea ssp. scapoidea (Synonyms: Camissonia scapoidea ssp. scapoidea, Camissonia scapoidea var. scapoidea, Oenothera scapoidea) -
Naked-stemmed Evening-primrose, Utah Suncup: Chylismia scapoidea ssp. utahensis (Synonyms: Camissonia scapoidea ssp. utahensis, Camissonia scapoidea var. utahensis) - ??
Wing-seeded Evening-primrose: Chylismiella pterosperma (Synonyms: Camissonia pterosperma, Oenothera pterosperma)
Alyssum-like Evening-primrose, Pine Creek Evening-primrose: Eremothera boothii ssp. alyssoides (Synonyms: Camissonia boothii ssp. alyssoides, Camissonia boothii var. alyssoides, Camissonia boothii var. villosa, Oenothera alyssoides, Oenothera boothii ssp. alyssoides) - Plants with stems present, with most leaves on the lower half of the stem. Petals white, at least 3 mm long. Stigma slightly longer than the anthers. Fruits often curved, or coiled.
Booth's Suncup, Booth's Evening-primrose: Eremothera boothii ssp. boothii (Synonyms: Camissonia boothii ssp. boothii, Camissonia boothii var. boothii, Oenothera boothii ssp. boothii, Oenothera boothii var. boothii)
Green River Suncup, Nelson's Evening-primrose, Small-flowered Evening-primrose: Eremothera minor (Synonyms: Camissonia minor, Oenothera minor, Oenothera minor var. cusickii, Sphaerostigma minor) - Plants with stems present. Leaves oblanceoltate to elliptic in shape with entire margins and alternate on the stems. Petals white, less than 1.5 mm long. Fruits sessile and contorted.
Dwarf Evening-primrose, Dwarf Suncup, Pygmy Evening-primrose: Eremothera pygmaea (Synonyms: Camissonia pygmaea, Oenothera boothii, Oenothera boothii var. pygmaea, Oenothera pygmaea) - Plants with stems present, the leaves over much of the lower half of the stem. Petals white, usually less than 3 mm long.
Blackfoot River Evening-primrose, Blackfoot River Suncup, Obscure Evening-primrose: Neoholmgrenia andina (Synonyms: Camissonia andina, Holmgrenia andina, Oenothera andina) - Flowering stems leafy, to 15 mm high. Plants branch from the base and are often wider than tall. The leaves are linear with entire margins and congested on the upper stems. Flowers yellow, the petals 1-2 mm long. Fruits spindle-shaped and less than 1 cm long, more than 1 mm wide.
Hilgard's Evening-primrose, Hilgard's Suncup: Neoholmgrenia hilgardii (Synonyms: Camissonia hilgardii, Holmgrenia hilgardii, Oenothera andina, Oenothera andina var. hilgardii, Oenothera hilgardii) - Similar to C. andina but with petals 2-3 mm long. In older keys (Hitchcock), this will key out as Oenothera andina.
Golden Eggs, Suncup: Taraxia ovata (Synonyms: Camissonia ovata, Oenothera ovata)
Diffuseflower Evening-primrose, Diffuseflower Evening Primrose, Long-leaf Evening-primrose, Long-leaved Evening Primrose, Stemless Evening-primrose: Taraxia subacaulis (Synonyms: Camissonia subacaulis, Jussiaea subacaulis, Oenothera heterantha, Oenothera subacaulis) - Stems absent or short and covered by the leaves and flowers. Leaves in a basal rosette with entire to lightly toothed margins. Flowers yellow. Stigma and anthers about the same height.
Tansyleaf Evening Primrose, Tansy-leaf Evening Primrose, Tansy-leaved Evening-primrose Taraxia tanacetifolia (Synonyms: Camissonia breviflora, Camissonia tanacetifolia, Camissonia tanacetifolia ssp. tanacetifolia, Oenothera breviflora, Oenothera tanacetifolia, Taraxia breviflora, Taraxia tanacetifolia ssp. tanacetifolia) - Plants with stems present. Leaves deeply pinnately lobed and arranged in a basal rosette. Flowers yellow. Stigma much longer than the anthers.
Palmer's Evening-primrose: Tetrapteron palmeri (Synonyms: Camissonia palmeri, Oenothera palmeri) -