Flower:

Flowers are densely packed in flat clusters about 1 inch across at the top of the plant, and at the end of stems branching from the upper leaf axils. Only a few flowers in a cluster are in bloom at one time. Individual flowers are about ¼ inch across and tubular with 2 lips. The upper lip has 2 lobes, but may look like 1. The lower lip has 3 lobes all about the same size. Color is white with purple spots. Inside the tube are 4 stamens with white tips that turn brown with age; the outside of the tube is covered in fine hairs.

Leaves and stem:

Leaves are up to 2½ inches long and ½ inch wide, toothless and hairless, tapering to a pointed tip, with a slightly rounded base and no stalk. Attachment is opposite. Stems are square with short hairs along the angles; color is green or reddish. Plants tend to create small colonies from short, spreading rhizomes.

Fruit:

Each flower produces 4 1-seeded nutlets.

Notes:

The leaves are strongly aromatic when crushed. Mature plants may have many branches and take on a bushy appearance. A similar species, Narrow-leaved Mountain Mint (Pycnanthemum tenuifolium), has a hairless stem and leaves not more than ¼ inch wide. It is not known to be in Minnesota but is present in Wisconsin.