An evergreen, semi-shrubby plant prostrate and woody at the base, 6 to 12 in. high, often reduced to tufts one-third those heights in dry, barren, rocky places; young shoots slender, wiry, erect, downy. Leaves opposite, crowded, linear to narrowly oblong, tapered towards both ends, 1⁄4 to 1 in. long, 1⁄12 to 1⁄6 in. wide, bright green and thinly downy above, grey-white with thick down beneath; margins decurved. Flowers densely packed in terminal, roundish clusters 1 in. across. Corolla 1⁄2 in. long, yellow, upper lip veined with purple; calyx tubular, downy, 1⁄4 in. long, with five teeth.
Native of the mountains of S. and S.E. Europe, north to parts of the Rhine-land and the Carpathians, etc., east to Asia Minor; in cultivation early in the 18th century. It is easily distinguished from T. chamaedrys by its clustered yellow flowers and narrow, usually toothless leaves. It flowers from July to September. In the Alps it is common on calcareous formations.
T. montanum belongs to the section Polium, of which the type is T. polium L., a variable species widely distributed in the Mediterranean region and once cultivated for its medicinal properties. The flowers are white or purplish red and the leaves always more or less crenated.