Holocarpha heermannii is a species of flowering plant in the aster family known by the common name Heermann's tarweed. It is endemic to California, where it grows in the hills, mountains, and valleys of the central part of the state. It is most common in the eastern San Francisco Bay Area and the southern end of the Sierra Nevada foothills. This is an annual herb growing mostly erect from 20 centimeters to over one meter in height. The stem is densely hairy and coated in short and long hairs. The leaves are up to 10 centimeters long near the base of the plant and those along the stem are smaller. The flower cluster is a spreading array of branches bearing clusters of flower heads. Each flower head is lined with phyllaries which are coated in large bulbous resin glands. They are hairy and sticky in texture. The head contains many yellow disc florets surrounded by three to 10 golden yellow ray florets. The ray and fertile disc florets produce achenes of different shapes.