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Jeruju or Sea holly
Acanthus sp.
Family Acanthaceae

updated Jan 2013
Where seen? These prickly plants with pretty flowers are often seen in thickets in the back mangroves, especially on mud lobster mounds. These plants have no relation whatsoever with the Christmas holly, although they appear similar. In fact, not all the leaves of a Sea holly plant may have spiny edges. Leaves growing the deep shade can be totally spineless.

Features: Sprawling shrub 50-80cm forming thickets up to 2m tall. Its sprawling growth allows it to spread by vegetative growth.

Leaves oval or eye-shaped (10-20cm) waxy, stiff. May be lobed and spiny or eye-shaped with a smooth edge. 'Spininess' appears to be a feature of younger leaves and may be affected by water stress, seasonality and light intensity. 'Acanthos' is Greek for 'thorny'. The plant gets rid of salt on its leaves, which can be encrusted in salt crystals in dry weather.

Flowers in clusters on an upright spike. According to Tomlinson, it appears to be pollinated by birds and large insects. The flowers have a structure and mechanism that allow the flower to pick up any pollen that is on the visitor's head, bill or body before depositing its pollen on the visitor as it departsSpr.

Fruit is a capsule (2-3cm) each with 4 flat, whitish seeds. The ripe capsule explodes, splitting violently and propelling the seeds like spinning discus up to 2m away.

According to Tomlinson, "they do not seem to differ in any consistent vegetative feature" and "there is a tendency to treat the mangrove species as one single variable species". Giesen also says that some authors regard the three species below as one highly variable species. But these species are usually differentiated in Singapore guidebooks.

Jeruju putih (Acanthus ilicifolius)
Open flower 3.5-4cm long, petals light blue or violet (rarely white). Inflorescence usually longer than 10cm. Ripe fruit 2.5-3cm or longer. Low sprawling shrub, not much branching, sometimes like a vine to 2m tall.

Jeruju hitam (Acanthus ebracteatus)
Open flower 2-2.5cm long, petals white. Inflorescence variable. Ripe fruit shorter than 2cm. Leaves usually widest below the middle. Usually with thick stems.

Jeruju (Acanthus volubilis)

Open flower 2-2.5cm long, petals white. Inflorescence variable usually shorter and with fewer flowers. Ripe fruit shorter than 2cm, but fruits are rare. Leaves usually wide above the middle. Usually with slender, sprawling stems without spines. It is more of a climber than the other species and in undisturbed forests may be seen even in the canopies.

Human uses: According to Burkill, the Malays have many medicinal uses for the plants and do not distinguish among the species. These include the seeds a part of cures such as cough-mixtures, as deworming for children and cures for boils. The pounded seeds used as a poultice on boils. The juice of the leaves are used to preserve the hair, the roots are used in a cure for shingles. A Malay ritual also includes using the prickly leaves under the house to ward off evil from pregnant women and using the leaves as part of rituals to heal mad people. According to Giesen, the fruit is pounded and used as a blood purifier and dressing for burns. Leaves relieve rheumatism. A compress of the fruit or roots is sometimes applied in cases of snakebite and arrow poisoning. Seeds are said to be used to treat internal worms. The plant may also be used as fodder.

Status and threats: A. ebracteatus and A. volubilis are listed as 'Vulnerable' in the Red List of threatened plants of Singapore.

Sometimes the same plant may have
spiky as well as smooth leaves.

Kranji Nature Trail, Jan 09

Exploded fruit capsule.
Kranji Canal, Mar 09

Flower structure to allow the flower
to pick up pollen from insect visitors
before deposting pollen as they depart.

Kranji Nature Trail, Jan 13

Kranji Nature Trail, Sep 09

Kranji Canal, Mar 09

Kranji Nature Trail, Jan 09

Sometimes scrambling up trees.
Pulau Ubin, Aug 09

Jeruju on Singapore shores

Photos of Jeruju for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map



  • Hsuan Keng, S.C. Chin and H. T. W. Tan. 1990, The Concise Flora of Singapore: Gymnosperms and Dicotyledons. Singapore University Press. 222 pp.
  • Corners, E. J. H., 1997. Wayside Trees of Malaya: in two volumes. Fourth edition, Malayan Nature Society, Kuala Lumpur. Volume 1: 1-476 pp, plates 1-38; volume 2: 477-861 pp., plates 139-236.
  • Tomlinson, P. B., 1986. The Botany of Mangroves Cambridge University Press. USA. 419 pp.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
  • Ng, Peter K. L. and Wang Luan Keng and Kelvin K. P. Lim, 2008. Private Lives: An Expose of Singapore's Mangroves. The Raffles Museum of Biodiversity Research . 249 pp.
  • Burkill, I. H., 1993. A Dictionary of the Economic Products of the Malay Peninsula. 3rd printing. Publication Unit, Ministry of Agriculture, Malaysia, Kuala Lumpur. Volume 1: 1-1240; volume 2: 1241-2444.
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