Pecut kuda in Latin is also called Stachytarpheta cayennensis. In Indonesia, it has many other names depending on the regional language where it is located. Internationally horsewhip is known as blue snakeweed, blue porterweed or Brazilian tea. In Java, this plant is also called jarong, gewongan or ngadi rengga.
Meanwhile, in France, this plant is known as herbe à chenille or herbe bleue, honagaso in Japan, selaseh dandi tree or snake tail tree in Malaysia and albaka or bilu - bilu in the Philippines.
S. Cayennensis orblue porterweed belongs to the Verbenaceae family which consists of around 100 parent species or genera. Stachy(s) (pointed tips, originally ears of corn) describe elongated inflorescences, and tarphy (thick) refers to thickened or densely flowered flower stalks. It takes its name from the capital of French Guiana, Cayenne (Nezet).
The genus Stachytarpheta contains about 65 species, most from the American tropics. Many of them are considered weeds throughout tropical and subtropical regions. The closely related species S. jamaicensis is similar to S. cayennensis and the common names for these species are often used interchangeably.
This plant comes from the American continent, especially Southern Mexico through Central and South America to Argentina and many of the Caribbean islands. Blue porterweed can also be found in other countries such as India, Australia, Florida region in the United States, the Philippines, Japan, and Indonesia.
Most of the introductions of these plants throughout the world are the result of deliberate introductions for ornamental purposes. S. cayennensis or blue porterweed produces blue flowers that are attractive to bees and butterflies. In 1868 the species was introduced to New Caledonia as livestock fodder (Nezet).
Blue porterweed is a perennial herb or shrub that can reach a height of up to 2.5 m. This plant has a bare, woody stem with several branches. The leaves are green all year round with opposite positions. It has an elliptical shape from a regular ellipse to a wide ellipse or oval with a length of 4 to 8 cm and a width of 2 to 4.5 cm (Nezet).
Blue porterweed flowers are purple or bluish purple. The flower petals are located on green stalks and have a scaly shape. The stem of this plant is included in the woody stem, even though it is relatively small. The entire surface of the stem is dark green the same color as the leaves. The stem of the plant also functions as a means of artificial vegetative reproduction, while generatively this plant reproduces using its seeds. Blue porterweed roots are a type of tap root.
Other species in the genus Stachytarpheta are very similar in appearance to S. cayennensis. These include S. jamaicensis, S. australis and S. mutabilis. The color of the flower is often used as a factor in distinguishing between species. The flowers of S. jamaicensis are light blue or light purple, S. australis has light blue or white flowers and the stems and underside of the leaves are pubescent where S. mutabilis is characterized by having larger pink or red flowers with hairy stems (Nezet).
Another difference between S. cayennensis and S. jamaicensis lies in the anatomical size of the leaves and stems in both species. In general, S. cayennensis has greater stem and leaf thickness than S. jamaicensis (Erhabor and Efosa). Another difference between the two species is that S. cayennensis usually grows upright while S. jamaicensis grows downwards (Flawildflowers).
Benefits and Uses of Blue Porterweed
Economically, since ancient times, the blue porterweed tree, especially because of its blue flowers, has often been used as an ornamental plant. In the Latin American region, horsewhip is used in traditional medicine to treat symptoms of malaria, treat dysentery and liver disorders, relieve fever, and act as a sedative. This plant is known to contain flavonoids, terpenes, phenols, and steroids and has been found to have anti-inflammatory and anti-malarial properties (Nezet).
Another benefit is as an animal feed ingredient. The use of blue porterweed as animal feed has been carried out since 1868 in New Caledonia.
Other Effects of Blue Porterweed on the Environment
In Australia, blue porterweed is considered an environmental weed with its properties capable of altering native habitats. Regulations have been implemented in several areas to prevent its spread. In New South Wales this species is restricted, meaning it cannot be sold or distributed within the region. In the Northern Territory, this species has been declared a noxious weed. This means that the spread of this species must be controlled and introductions prohibited.
The blue porterweed is on the list of the 33 most invasive species in the South Pacific. Its presence is increasingly abundant in Florida, USA. According to the risk assessment, this species is considered highly invasive with high risk (Nezet).