[explorer.natureserve.org] Rarity: Hesperolinon sharsmithiae occurs in the western United States where it is endemic to serpentine soils of Lake and Napa counties. There are 35 known occurrences, of which a third are on private lands where they are threatened by development and expansion of vineyards. Surveys are needed to determine how occurrences with the threat of land conversion are doing. Some occurrences are on BLM land and State Park lands. (link added by Mary Ann Machi)

[wildflower.org] Description: Plant Characteristics Duration: Annual Habit: Herb Leaf Arrangement: Alternate Leaf Shape: Linear Leaf Margin: Entire Inflorescence: Axillary , Cyme Fruit Type: Capsule Size Notes: To about 20 inches in height. Leaf: "Leaves alternate; stipular glands present only at proximal nodes; blade linear, 15 to 20 by 1 to1.5 mm, base flat, not clasping, margins without stalked glands." (Webref: 3). Flower: "Inflorescences: cymes dichasial, open, internodes long, flowers scattered; bract margins sparsely glandular. Pedicels 0.5 to 2 mm near tips of branches, 4 to 5 mm in fruit, ascending, not bent at apex. Flowers: sepals erect, not reflexed at tip, oblanceolate, (1.5-)3 mm, equal, margins sparsely glandular, surfaces glabrous; petals widely spreading, yellow, veins sometimes red-streaked, oblanceolate to obovate, or almost oval, 3 to 4.5 mm, apex erose; cup yellow, rim lobed between filaments and petal attachments; stamens exserted; filaments 1.5 to 2.5 mm; anthers yellow, dehisced anthers 1 to 1.5 mm; ovary chambers 6; styles 3, color not known, 2 to 3.5 mm, exserted." (Webref: 3). Fruit: "Fruit globose capsule about 2 mm long and as wide." (Reslit: 3182). Bloom Information Bloom Color: Yellow Bloom Time: May , Jun , Jul (link added by Mary Ann Machi)