San Joaquin Woolly-threads

San Joaquin woolly-threads is found in non-native grassland, valley saltbush scrub, interior coast range saltbush scrub and upper Sonoran subshrub scrub communities. It grows in neutral to sub-alkaline soils. On the San Joaquin Valley floor, this species typically is found on sandy or sandy loam soils, whereas on the Carrizo Plain, it grows in silt rich soils. San Joaquin woolly-threads also grows in sand dunes and on sandy ridges, as well as along the high-water line of washes and on nearby terraces. This species has been found in elevations ranging from 200 to 2,600 feet.

San Joaquin woolly-threads is a small flowering annual in the sunflower family. Most parts of this plant are very little, with most of the plant often being less than 3 inches wide, except for the long, trailing stems covered with tangled hairs from which it gets its name, which can be up to 18 inches long. It has tiny yellow flower heads that are 0.25 inches long, but despite the small size, each flower head has many flowers within it. The leaves are narrow and lobed, and covered in pale woolly fibers.

Seeds may sprout as early as November, but more often in December and January. San Joaquin woolly-threads typically flowers between late February and early April, and do not seem to require insect pollination. Each plant may have anywhere from 1 to 400 flower heads. Tiny yellow flower heads are clustered at the tips of the stems and branches. Each flower head is about 0.25 inches long, and has two types of even tinier flowers: four to seven ray flowers and numerous inner disc flowers. The two types of flowers produce one-seeded fruits that also differ in shape. The number of seeds a plant makes depends on plant size and the number of flower heads but can range from 10 to 2,500 seeds. In April or May, once the seeds are dropped, the plant dies and dries up becoming unnoticeable on the landscape.