Joe Pye weed (Eupatorium purpureum) is found throughout the central and eastern United States in Zones 5 to 9. The plant is a perennial herb. It easily grows up to 7 feet in height with a 3-foot spread. Pink, fragrant 8-inch flower corymbs begin to appear in July that are favored by butterflies and bees. The plant's root system is popular when crushed and used as a diuretic tea. The plant received its name from a New England medical man who used the roots to treat typhus, according to Kansas State University.
The plant thrives in moist to wet soil conditions where it grows an abundance of fibrous roots that often form rhizomes. Rhizomes are large, fleshy horizontal roots that grow tiny feeder roots off the large rhizome.The roots of the Joe Pye weed are a purplish color with fleshy cream colors inside. They are relatively shallow and normally grow no deeper then a foot but have a very large and diverse spreading habit.
The rhizomatous roots form large colonies of the plant in their vast horizontal spread. They can easily be dug up and transplanted to new locations. The plant also propagates by seeds which are widely dispersed by the wind. Seeds will germinate when the temperature is above 55 degrees Fahrenheit. Germination occurs 30 to 90 days after planting. The seeds do require a three-month cold stratification with a temperature of around 40 degrees Fahrenheit prior to planting.
The plant collects nutrients and stores water within its rhizomatous roots. When the ground freezes and winter arrives, the plant's top growth dies back but the roots maintain the plant's ongoing life during the cold months. When spring arrives, new top growth erupts from the root system.
The roots of the Joe Pye weed are harvested in the winter to be used in numerous herbal medications and teas which are widely believed to treat kidney problems, menstrual discomforts, reduce fever and aid in childbirth. The roots of the plant are easily dug up using a shovel. The top growth is discarded in the fall and only the roots are used. During the spring months the new foliage is often harvested and used in medicinal tinctures.
The Joe Pye weed is often successfully grown as a container plant. The root system must be kept constantly moist. If the fibrous roots are allowed to dry out in a container in the hot summer months, the plant will easily perish. When grown as a container plant the Joe Pye weed grows only to a height of 2 to 4 feet.