Individual flowers have five or six pink-purple petals surrounding small, yellow centers.

Each flower spike is made up of many individual flowers. 

Leaves are downy, with smooth edges.

They are usually arranged opposite each other in pairs which alternate down the stalk at 90 degree angles, however, they may appear in groups of three. 

Stalks are square, five or six-sided, woody, as tall as 2 meters (over 6 feet) with several stalks on mature plants.

On mature plants, rootstocks are extensive and can send out up to 30 to 50 shoots, creating a dense web which chokes out other plant life.