The overall size varies between species from 30 cm tall up to 2 m tall. The leaves are entire, opposite and decussate (each leaf pair at right angles to the next) and rugose or reticulate veined. The bracts (floral leaves) are similar or different from the lower leaves. All parts are frequently covered with hairs. The bracteoles are ovate, lanceolate or linear. The flowers are arranged in whorls called verticillasters which encircle the stems. The stems are usually square in section with rounded corners, although tomentum on the stems can make them appear circular. The colour of the flowers varies from yellow to pink, purple and white. The calyx is tubular or campanulate with five or ten veins visible. Five teeth, either all equal or with the outer two longer than the others. The upper lip is hood shaped and laterally compressed (P. tuberosa, however, has an uncompressed lip with a dense bearded edge). The lower lip is trifid, the central lobe being larger than the lateral ones. There are four stamens ascending under the upper lip. Anther with forked end, the upper fork being shorter than the lower. The fruits are four three-sided, nutlets, and sometimes topped with hair, sometimes glabrous. The root system can be very extensive; roots of 6-week-old seedlings have been measured at 0.7 m.
The name Phlomis derives from a Greek word for "flame", and may refer to the leaves' use in ancient times as lamp wicks.
Barcode of Life Data Systems (BOLD) Stats Specimen Records:86 Specimens with Sequences:90 Specimens with Barcodes:22 Species:27 Species With Barcodes:27 Public Records:82 Public Species:26 Public BINs:0