Alhagi is a small genus of spiny shrubs in the legume family Fabaceae (order Fabales), commonly known as camelthorns or manna trees. The genus comprises four accepted species native to the Old World, ranging from northern Africa and Greece across western and central Asia to India and northern China, with one outlier species (A. brevispina) found in the Tibesti Mountains of Chad.
The most distinctive feature of Alhagi species is their extraordinary root system: a shrub barely 1 m tall may extend a taproot more than 15 m into the ground. This adaptation makes them drought-avoiding rather than drought-tolerant — they track the water table rather than withstand desiccation — and allows them to thrive in hyper-arid habitats where few other plants survive.
Alhagi species are ecologically and culturally notable as hosts of a scale insect whose secretions produce a sugary exudate known as Tarangabeen or Manna of hedysarum, long used in Persian and Central Asian traditional medicine, particularly as a remedy for neonatal jaundice. The genus name derives from the Arabic word for "pilgrim," and in Persian the plant is called خارشُتُر (xâr-e šotor), meaning "thistle of camels" — a reference to the ability of camels to browse the spiny foliage. The larvae of several moth species, notably Coleophora argyrella (which feeds exclusively on A. maurorum), also rely on Alhagi as a host plant.
Etymology
The genus name Alhagi derives from the Arabic word for "pilgrim." In Persian the plant is called خارشُتُر (xâr-e šotor), meaning "thistle of camels," reflecting the ability of camels to browse the thorny shrubs.
Distribution
The four Alhagi species range from northern Africa and Greece through western and central Asia to India and northern China. A. brevispina is restricted to the Tibesti Mountains of Chad; A. graecorum spans Greece, western Asia, the Arabian Peninsula, and North Africa; A. maurorum occurs from the Levant and Caucasus to central Asia and Xinjiang; and A. pseudalhagi extends from North Africa and Greece to the western Himalayas and northern China.
Ecology
Alhagi species grow in hyper-arid and semi-arid habitats, surviving extreme aridity by means of exceptionally deep root systems — a 1 m shrub may have a taproot exceeding 15 m — which allow them to access groundwater. The spiny foliage is browsed by camels and supports larval populations of Lepidoptera including Coleophora argyrella, which feeds exclusively on A. maurorum. The plants also host a scale insect whose honeydew secretions form the traditional exudate Tarangabeen.
Cultural Uses
Alhagi species have been used in Persian and Central Asian traditional medicine for centuries. A scale insect that lives on the foliage produces a sweet exudate called Tarangabeen or Manna of hedysarum, which is used as a remedy for neonatal jaundice. Camels are well-known browsers of the thorny stems, which gave rise to the Persian common name meaning "thistle of camels."
