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Physic Nut (Jatropha curcas)

Physic nut or Jatropha curcas is an erect small flowering shrub or tree usually growing 2-4 meters tall. 

It has been mainly cultivated as a hedging plant around mining sites and homesteads in northern Australia.

Traditional medicine uses the plant’s leaves and bark to treat various ailments, including fever, jaundice, and dysentery. 

Scientific Classification  

  • Kingdom: Plantae  
  • Phylum: Tracheophyta 
  • Class: Magnoliopsida
  • Order: Malpighiales
  • Family: Euphorbiaceae
  • Genus: Jatropha
  • Species: Jatropha Curcas
  • Common Names: Barbados nut, American purging nut, Barbados purging nut, Black vomit nut, Brazilian stinging nut, Cuban physic nut

Nativity and Distribution

Jatropha curcas establishes itself on disturbed land like mining sites, semi-arid rangelands, and roadsides. The plant is native to the following areas:

  • Mexico  
  • Central America  
  • Caribbean Islands
  • South America

Physical Appearance

Jatropha curcas has large dark-green leaves, thick stems, and oval-shaped fruits
Jatropha curcas has large dark-green leaves, thick stems, and oval-shaped fruits. Image: Canva/tanesimages
  • Leaves: Large, shiny, dark green leaves 10-15 cm long and arranged alternatively on stems. 
  • Flowers: Small, green, and yellowish-white flowers in clusters on short stalks. 
  • Stems: Stems are thick, softwoods; younger trees may have hairy stems. 
  • Fruits: Oval or round fruits 3-4 cm long and contain three black or brown seeds. 

Jatropha curcas leaves are smooth in texture and are kidney-shaped. They are 17-20 cm long and 5-15 cm wide and held on long stalks. 

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Leaf margins are irregular, and the leaf base is heart-shaped and supports 3-5 lobes and 3-5 veins.

Physic nut is monoecious with female and male flowers on the same plant. Female flowers occur singly, while the male flowers are arranged in an inflorescence called a cyme.

The plant’s stems are gray-green and have extensive branches. In young plants, the stem is covered by a green hairy bark and, when old, a light brown bark.

When cut, the stem produces milky sap, colorless in younger branches.

Life Cycle/ Reproduction/Dispersal

  • Life Cycle: Perennial.
  • Seeds: Seeds are fleshy capsules that are green in color and turn yellow and dark brown when mature.
  • Climate: Thrives in tropical and subtropical regions.
  • Dispersal: Seeds are dispersed by explosive release, water birds, plants, and animals.

The plants germinate at the onset of the wet season, usually between October and December. Growth is rapid during the wet seasons and slow during the dry season.

Jatropha curcas flowers throughout the year but are most robust during the wet season. The plant is deciduous and sheds leaves during the dry season.

Physic nut seeds may be spread for short distances or long-range dispersal in water or mud that adheres to animals or vehicles. Deliberate cultivation in some homesteads may also spread the species.

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Uses

The Physic nut seeds can treat various illnesses and create biodiesel fuel
The Physic nut seeds can treat various illnesses and create biodiesel fuel. Image: Canva/ziprashantzi

Medicine

    According to a 2013 study published by PubMed Central, the physic nut effectively treats the influenza virus.

    Jatropha curcas seeds’ purgative oil has also been used to cure various illnesses, including rheumatism, syphilis, and skin disorders. 

    The plant’s leaves contain chemicals such as apigenin, vitexin, and isovitexin, which treat muscular aches and malaria.

    Even though the plant is toxic, physic nut seeds may have anti-cancer capabilities at non-lethal levels.

    Biofuel

      Jatropha curcas seeds have an oil content of about 27–40% (average: 34.4%), which can be refined to create biodiesel fuel. 

      The oil from the seeds is a renewable energy source that can replace kerosene and diesel. It is still utilized for street lighting and other uses, having been used in engines during World War II.

      Making dyes

        Tannins found in the plant’s bark and leaves are used to create a dark blue dye. In Ghana, people tan leather using the plant’s seeds.

        Pest control

          The bark of the physic nut has insecticidal and fungicidal properties and has been used to control certain pests such as aphids, mealybugs, whiteflies, and spider mites.

          Impact on Environment

          Jatropha affects the environment in various ways:

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          Environmental weed

            Physic nut is considered an environmental weed in many parts of northern Australia. The plant is drought-resistant and will grow in various climatic and soil conditions.

            It is usually found in disturbed areas, especially mines and abandoned homesteads.

            The plant competes with native species or pasture plants and can eventually form dense thickets or colonies. It may also act as an alternative host for insect pests of cotton crops.

            Toxicity

              Jatropha curcas seeds contain toxic lectin dimers and carcinogenic phorbol esters, making this fruit poisonous for human consumption and livestock.

              The plant’s sap is a skin irritant, and ingesting at least three untreated seeds can prove fatal to humans. 

              Control

              The following control methods can be used to control the Physic nut:

              Digging out

                An individual plant can be dug out and burnt, removing as much of the tuberous root system as possible. 

                Chemical herbicides

                  Herbicides such as Metsulfuron, Fluroxypyr, and Picloram are recommended to control Jatropha curcas

                  They should be applied during the wet season when adequate moisture is present, and the plants are actively growing.

                  Large plant colonies of physic nut can be controlled with the cut stump method, in which the plant is cut off close to the soil surface, and immediately, an herbicide is applied to the cut surface.