Naming Identity

Kirinyu or also known as rumput minjangan in Indonesia is scientifically known in Latin as Chromolaena odorata L.

Internationally known as Siam weed. In Spanish this plant is known as chimuyo, devilweed in Australia and pokok german in Malaysia.

Taxonomy

Origin and Distribution

Siam weed is a plant originating from the neotropics that grows naturally in the southern United States, the Caribbean, along the waters of the Amazon River in South American countries, southern Brazil and Paraguay. From its area of origin, this plant was then distributed to other regions in Africa, Australia, South Asia and Southeast Asia, including Indonesia.

This plant was first introduced in Calcutta, India in 1840 as an ornamental plant and then continued to spread to other Asian regions including Malaysia, the island of Sumatra in Indonesia, and the Indo-China region in the 1920s.

Siam weed has been a weed plant since its initial cultivation in Africa in the 1940s. Meanwhile, in Australia, Siam weed was only discovered in July 1994 in grazing areas on the Tully River, Queensland (Scott, 1998).

Shape Description

Often considered the world's worst weed because it can reduce grazing capacity, Siam weed is an annual herbaceous plant that can grow very thickly quickly. Its height can reach up to 20 meters by occupying land or by climbing over adjacent vegetation. However, generally, this plant can grow up to 1.6 to 3 meters high.

The slender stems are usually yellowish-green and somewhat hairy, but become woody at the base of the plant. The stems can grow up to approximately 7 meters.

Siam weed has many branches, with lateral branches usually produced in pairs at the base of the leaves. The leaves are arranged in opposite directions with a length of 5 to 12 cm and a width of 3 to 7 cm, triangular or oval-shaped like a round egg, and have a pointed tip.

The leaves are hairy (pubescent) on both surfaces and have coarsely toothed or serrated margins. The leaves rest on stems or petioles that can reach up to 6 cm (usually 10-15 mm) in length, and emit a pungent odor when crushed.

The flower heads are small (capitula) and have no 'petals' or florets and are borne in dense clusters at the ends of the branches. The flower heads, which are about 10 mm long and 3 mm wide, are pale pink or pale purple (sometimes appearing whitish when older) and consist of many small flowers or tubular florets.

These small flowers between 10 to 12 mm long are surrounded by several layers of overlapping slender bracts (involucre) 8 to 9 mm long. Each flower head (capitulum) is borne on a stalk or flower stalk that is 10 to 30 mm long. It has black or dark brown seeds (achenes) with a length of 4 to 5 mm which are found at the top with a ring (pappus) of white to brownish hairs which are between 5 and 6 mm long.

Why does Siam Weed Said to be the Worst Weed in the World?

Its growth characteristic, which can grow quickly by invading land and creeping over other vegetation, makes it a bad weed. Apart from being an aggressive competitor, Siam weed is also thought to have an allelopathic effect that causes poisoning and even livestock death.

Benefits of Siam Weed

Although declared the world's worst weed, Siam weed also has several agricultural and medical benefits in traditional medicine. According to a research journal conducted by M. Thamrin through the Swamp Agricultural Research Institute, Siam weed has been proven to be a vegetable insecticide because it contains pryrrolizidinealkaloids which are toxic to insects. Research was carried out mainly on armyworms as pests that are difficult to control because of their rapid reproduction.

Meanwhile, based on the results of research conducted by Bambang Nugroho through studies at the Agrotechnology Study Program, Faculty of Agroindustry, Mercu Buana University Yogyakarta, Siam weed has been proven to be able to help in the development of organic shallot farming by using the Siam weed plant as compost.

Traditionally, especially in Malaysia where this plant is also said to be an invasive weed, parts of the plant are used to treat burns, wound healing, skin infections, post-natal wounds, and as an anti-malarial drug. Some medical studies have also confirmed that Siam weed leaf extract has certain anti-microbial, anti-inflammatory and wound-healing effects, and has been identified as a potential source of human medicines (Pasiecznik, 2022).