Photo: Chuck Hubbuch
Porterweed is a common name for plants in the genus Stachytarpheta. Some of these plants are cultivated for their attractive flowers and their traditional medicinal uses. Some for so long that their origins are no longer clear. Names of these cultivated species are commonly confused in literature and nurseries. Most are tropical and serve well as summer annuals in Jacksonville. One is a perennial, tolerating winter temperatures in the upper teens Fahrenheit.
With some searching, four species can be found in Florida. All of them produce flowers that are very attractive to butterflies and hummingbirds. The name, Stachytarpheta jamaicensis has been confused with more than one species by various authors. Commonly known as blue or native porterweed, the true Stachytarpheta jamaicensis is native to Florida and the Caribbean. It is a low-growing plant with lavender flowers. Stachytarpheta cayanennensis (previously known as S. urtifolia) is probably native to the American tropics but is widespread now in the world’s tropics. Its common names include blue snakeweed because of its long slender flower spikes or nettleleaf porterweed. It is an upright plant to three or four feet tall with dark blue flowers. This species is used in traditional medicines in the Americas and Asia – especially for respiratory problems, fever and liver disorders. Stachytarpheta microphylla is the red porterweed. Frequently called Stachytarpheta sanguinea in garden literature and the nursery trade, it is a compact plant with red flowers. These three flower through the summer and are great summer annuals here. They may survive mild winters but are not reliably cold hardy in Jacksonville.
Stachytarpheta mutabilis is called coral porterweed, giant porterweed, pink snakeweed and even changeable velvetberry (by the USDA). This species grows to six feet tall or more. Its flowers are coral-pink to royal purple in color. A plant of this species is in the pollinator garden at the Jacksonville Arboretum and Gardens. It flowers hold a great attraction for butterflies, moths, hummingbirds and other pollinators. In local gardens, a few seedlings volunteer near the parent but the plant has not spread aggressively. Although most references state that this is a plant for south Florida (USDA Zone 10), this species has proven to be cold hardy to brief winter drops into the upper teens Fahrenheit. It may die back in winter but will return from the crown in spring. In traditional medicine, its leaves are reported to have been used as an external treatment for wounds, as an internal treatment for intestinal worms and as a laxative.
By Chuck Hubbuch