Thursday, January 19, 2012

Sea Holly (Acanthus spp.)

Singapore has 3 species of Sea Hollies (Acanthus spp.) from the family Acanthaceae in our mangrove forests - Acanthus volubilis, Acanthus ebracteatus and Acanthus ilicifolius. The former 2 have the status of "vulnerable" while A. ilicifolius is a common species.

They generally occur along tidal rivers, in the mangrove forest or nearby, especially in areas with freshwater inputs or on mud lobster mounds.

Acanthus volubilis occurs as a bush-like, sprawling herb, or when there are other taller structures around, as a climber.

It has simple opposite leaves that has pointed tips when they are growing in areas exposed to the sun, but become more rounded when they are growing in the shade. The flowers are white.

Acanthus ilicifolius and Acanthus ebracteatus occur as low, sprawling herbs and seldom climb. Young plants generally have erect stems, but lean and sprawl as they mature.

Plants growing in areas exposed to the sun tend to have spiny leaves. The 2 species can be differentiated by the colour of their flowers. Acanthus ebracteatus has white flowers.

Meanwhile, Acanthus ilicifolius has purple flowers. For both species, the leaves have smaller spines or no spines when the plants are growing in the shade.

The leaves often appear moist, especially in the morning before it got too hot, as Acanthus spp. excrete excess salt through their leaves. Sometimes, tiny salt crystals can be seen on the leaf surfaces.

Sea Holly fruits are small nut-like capsules.

Leaves of Acanthus ilicifolius and Acanthus ebracteatus are used to treat rheumatism, while the fruit and roots are used to treat snake bites and as poisons for arrows. The seeds are used to treat internal worms. Seeds of Acanthus volubilis are used for blood cleansing medicine and against ulcers.

  • Chong, K. Y., H. T. W. Tan & R. T. Corlett, 2009. A Checklist of the Total Vascular Plant Flora of Singapore: Native, Naturalised and Cultivated Species. Raffles Museum of Biodiversity Research, National University of Singapore. Singapore. 273 pp.
  • Giesen, W., S. Wulffraat, M. Zieren & L. Scholten. 2006. Mangrove guidebook for Southeast Asia. RAP Publication 2006/07. FAO Regional Office for Asia and the Pacific & Wetlands International. Bangkok. 769 pp.
  • Ng, P. K. L. & N. Sivasothi. 1999. A guide to the mangroves of Singapore 1 : the ecosystem & plant diversity. Singapore Science Centre. Singapore. 168 pp.

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