Threadleaf Phacelia

Threadleaf phacelia (Phacelia linearis) is a native annual found in the western half of Canada and the United States, particularly in the Great Basin. Its habitat is sagebrush scrub and dry, open gravely slopes and flats mostly between 3,000 and 6,000 feet.

The form of the plant depends on the amount of rainfall. In moist years the plants are tall, branched and have many flowers. In dry years or in especially dry environments threadleaf phacelia is small and unbranched with one or a few flowers. The stiffly erect stem, like all of the herbage, is hairy.

The alternate leaves are linear, but often are three-lobed. The leaves are sessile (not stalked) or nearly so.

The threadleaf phacelia inflorescence is a coiled cyme (branched with the uppermost flowers maturing before the lower ones) of purplish to nearly white flowers. The broadly bell-shaped flowers have five petals fused at the base, narrow sepals, and five protruding stamens.

Threadleaf phacelia fruits are small lance shaped to ovid capsules containing 6 to 15 oblong seeds with pitted surfaces.

Most references (including Oregon Flora) place threadleaf phacelia in the Waterleaf Family (Hydrophyllaceae). Cal Flora/Jepson Herbarium list it as a member of the Borage Family (Boraginaceae). I am not certain where it belongs.

Sand phacelia, threadleaf scorpion weed, Carson’s phacelia, and linear-leaved phacelia are some of the other common names by which P linearis is known.

These specimens were growing in May either along Road 8A between Fish and Gooch Springs in Sheldon National Wildlife Refuge (Nevada) or along the Thomas Wright Battlefield Trail at Lava Beds National Monument (California).

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