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Sea holly, also known as holly mangrove or holly-edged Acanthus, is a shrub-like plant with either purple or white blooms. Its leaves are sharp and prickly, nearly resembling the spiny-edged leaves of holly shrubs. The plant belongs to the genus Acanthus, which is native to parts of India and onwards through Polynesia and Australia. The genus consists of two species: A. ilicifolius and A. ebracteatus.
Normally growing along muddy areas near high tide edges or river banks, sea holly can cover large areas with its adventitious root system, forming thickets or undergrowth within mangroves. The plant may also be found growing beneath trees and occasionally in open areas as well, though it prefers to be located in freshwater areas. Holly mangrove is an interesting plant to say the least with multiple uses.
One of the characteristics that set this shrubby plant aside from other mangrove plants is its salt-secreting trait. Most mangrove plants secrete excess salt at the roots. Sea holly, on the other hand, does not. Instead, its salty sap is emitted through the leaves. This white, crystal-like substance is then washed away by rain or wind.
Holly mangrove has provided a number of traditional or folkloric uses among certain native people groups. For instance, the plant was believed to guard one against snake bites or to ward off evil. The thorny leaves were once used to provoke crying in newborns following birth. Parts of the plant found use in hunting as well. The plant also provided food and cover for some animals.
In addition, sea holly has provided its share of medicinal use. In fact, it has even been called an "Indian medicinal plant” by some. Both species have been used to treat kidney stones by boiling the entire plant and drinking the liquid. Tea made from the leaves was thought to help purify the blood as well as relieve pain.
The leaves from the purple-flowered species, A. ilicifolius, were commonly used as a treatment for rheumatism. Malaysians also sought out the leaves for healing wounds inflicted by poisoned arrows. The crushed seeds from the white-flowering species, A. ebracteatus, were used for treating boils. Both species of sea holly were employed as hair tonics to prevent baldness.
The bark of both species was also employed for medicinal purposes. An extract was given to treat colds and skin conditions brought about by allergic reactions. When ground into powder form, the bark was often used as an antiseptic for wounds. Today, the sea holly plant is being studied for its possible cancer-fighting properties within the liver.