The overall size varies between species from 30 cm tall up to 2 m tall (12–79 in). 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.
Phlomis species are the only host plants of the moths
Coleophora phlomidella and
C. phlomidis.
Phlomic acid is named after the genus. == Systematics ==