The holly-like leaves of Acanthus ebracteatus.

With their spiky serrated leaves, Sea Hollies resemble Christmas hollies. You can celebrate this Christmas by growing a native sea holly at home. Sea Hollies is the common name given to the Acanthus species that are found in mangrove forests. In Singapore, three Acanthus species are recorded:

a. Acanthus ebracteatus
b. Acanthus ilicifolius
c. Acanthus volubilis

The three native Acanthus species are hardy, shrubby, herbaceous plants or climbers typically found in - mangrove forests away from the river or water source. While they can grow up to 2 metres tall, they typically remain short and shrubby, up to 1 to 1.5 metres tall. This genus is known for its erect, spreading growth habit; thorny spines and upright flowering spike

Acanthus ebracteatus, a shrubby back-mangrove plant growing along Changi creek.

From left to right: Acanthus ebracteatus with white flowers and holly-like leaves; Acanthus volubilis with white flowers and oval leaves that are smooth-margined; and Acanthus ilicifolius with pale-violet flowers and leaves that are smooth-margined or holly-like.

Sea Hollies are readily available at larger plant nurseries in Singapore. They are cultivated for their spikes of ornamental flowers, which range from white to pale purple in colour, and also for its foliage which closely resembles holly leaves. As insects and sunbirds are attracted to the flowers for their nectar, Sea Hollies make a nice addition to one’s garden.

For most gardeners, they are relatively easy to grow and require minimal maintenance. Here are some tips to ensure a thriving and happy plant:

Light
Sea Hollies generally do very well under full sun to partially-shaded conditions, where they grow lush and bushy. While they can tolerate semi-shady environments, they tend to become leggy in shape.

Soil
A standard potting mix readily available off the shelves at any florist shop or nursery is adequate for Sea Hollies to grow well. Although they are tolerant of waterlogged soils, heavy or clay soils are generally not recommended.

Water
Sea Hollies grow naturally on the mudflats of back mangroves, where they experience flooding twice a day. When growing the plant in your home, water it at least once daily as it does not tolerate completely dry soils. This is one plant you can occasionally overwater.

Nutrient
Growing in nutrient-rich environment, Sea Hollies can be fed with any store-bought liquid or dry fertilisers which should be applied when needed. Be careful not to over apply as it may cause ‘root burn’ and kill the plant. Always follow the recommended application dosage/dilution as stated on the packaging.

Propagation
These hardy plants can be easily propagated via seeds or stem cuttings. Stem cuttings are usually preferred as the cuttings can be obtained easily from prunings. These cuttings should be placed under a semi-shaded environment and watered regularly until the roots show.

Acanthus ebracteatus
Common name: Sea Holly, Jeruju, Jerujah, Jeruju Hitam, Holly-Leaved Mangrove
Chinese name: 小花老鼠勒
Description: It is a sprawling herbaceous plant that grows up to 2 metres tall, but usually remains shrubby, at about 1.2–1.5 metres. Its stalked leaves are oblong in shape, with distinctive lobed margins and spiny tips which are a shiny dark-green above, and are 7.5–20 cm long. The white flowers are borne on upright flowering shoots that are 8–15 cm tall. The fruits are green capsules that are 2–3 cm long. It is listed as ‘vulnerable’ in the wild as it is not as common as the other two species.

Acanthus ilicifolius
Common name: Mangove Holly, Sea Holly
Chinese name: 老鼠勒
Description: It is a sprawling herbaceous plant that can grow up to 3 metres tall, but usually remains shrubby, about 1.2–1.5 metres. Its stalked leaves are oblong in shape, with distinctive lobed margins and spiny tips which are a shiny dark-green above, and are 7.5–20 cm long. The pale-lilac flowers are borne on upright flowering shoots that are up to 20 cm tall. The fruits are green capsules that are 2–3 cm long. It is common in its natural habitat in Singapore.

Acanthus volubilis
Common name: Jeruju
Description: It is an herbaceous climber that can grow to about 2 metres tall. Its stalked leaves are elliptic to lanceolate, with smooth margins, and are 15 cm long and 2.5–2.9 cm wide. The white flowers are borne on upright flowering shoots. The fruits are green capsules. It is vulnerable in its natural habitat in Singapore. Another type of Sea Holly (below), which is the variegated version of Acanthus ebracteatus, is also readily available in commercial nurseries. The green foliage with whitish-cream colour patches makes this variegated Sea Holly an even more attractive plant to have around the house.

You can add Christmas ornaments to your Sea Holly to give it a festive touch.

So start growing your own Sea Hollies for Christmas!

By Arthur Ng & Ang Wee Foong
Photo credit: Dr Jean Yong and NParks Flora & Fauna Web (http://florafaunaweb.nparks.gov.sg)