This perennial plant is 3-7′ tall and usually unbranched. The central stem is light green and glabrous, except where the whorls of leaves of occur, where it is slightly swollen and purple. There are 3-4 leaves in each whorl along the stem. The leaves are about 6″ long and 3?” across, or sometimes larger; they are broadly lanceolate or ovate and crenate-serrated along the margins. Each leaf is dull green and hairless on the upper surface; the lower surface is pale green and hairless to finely pubescent. The foliage may be vanilla-scented, although this varies with the local ecotype