Thursday, July 12, 2012

Coastal Shrubs & Trees with Compound Leaves in Singapore

Thought I'll share about how I identify the shrubs and trees with compound leaves that I have seen around Singapore's coastal areas. The descriptions are more for mature plants, as young plants may not be exhibiting all the distinguishing characteristics. Also, this guide can only be used in Singapore, as the same species may exhibit a different growth form in other countries.

A compound leaf is one with a leaf blade fully subdivided into leaflets. Each leaflet is attached to either a main or secondary vein. The leaflet can be mistaken as a simple leaf, and hence to differentiate them, one will need to identify where the petiole (the leaf stalk attaching the leaf blade to the stem) occurs. The petiole can usually be broken easily from the stem, and often there will be outgrowths occuring on each side of the petiole, called stipules. It is possible to differentiate compound leaves and simple leaves by looking at the new leaves - a new compound leaf will occur as one with many small new leaflets, while new simple leaves will occur as individual new leaves.

Generally, shrubs refer to plants that are short (no more than a few metres tall) with a few woody stems, while trees are taller with one main woody stem. As some young trees may appear shrubby, I have decided to put both shrubs and trees together here.

This seashore environment is a very harsh environment for the trees and shrubs growing there. It is usually very dry, due to the land and sea breeze which increases the rate of evaporation. It is especially dry on rocky and sand shores since the substrates are rather porous. Salt sprays from the sea also have a drying effect on the plants living there. These coastal shrubs and trees, unlike true mangrove plants, are usually found in areas seldom or not inundated such as the back mangroves. Hence, they are also called mangrove associates. Many of them can also be found growing in other types of seashore ecosystems, such as sandy or rocky shores.

Note that this guide is only meant for mature plants, since young plants such as saplings may exhibit a different morph. To identify the tree/shrub, just go through the following questions:

A) The leaf has less than 10 leaflets (no secondary leaflets)?
B) The leaf has 10 or more leaflets (no secondary leaflets)?
C) The leaflets are subdivided into secondary leaflets?

A) Leaf has less than 10 leaflets that are not subdivided into secondary leaflets.

1. The leaf is trifoliate with elliptic or narrowly obovate/ovate leaflets.

Mangrove Tit-berry (Allophylus cobbe)
Mangrove Tit-berry (Allophylus cobbe) - This shrub has small white flowers hanging in bunches, and the smooth, round and juicy fruits turn bright orange to red as they mature. It usually occurs in the back mangrove in areas not affected by the tides. The fruits are edible, but the wood is of poor quality and is mostly only used for firewood or roofing. Like most other legumes, it has nitrogen fixing bacteria in its root nodules, and helps to improve the soil for other plants to grow.

2. The leaf is trifoliate with broadly ovate/obovate leaflets.

Horse Bush (Dendrolobium umbellatum)
Horse Bush (Dendrolobium umbellatum) - This plant may occur as a shrub or tree, and usually occurs on sandy or rocky shores, and occasionally at the back mangroves. The stem may have numerous lenticels. The inflorescence is white, occuring at the leaf axils. The seed pods are curved. The leaves have hairy undersides, and can be eaten or made into a tonic drink.

3. The leaf has one or two pairs of leaflets, and each leaflet is asymmetrically elliptic, i.e. one side of the leaflet has a bigger surface area than the other side.

Katong Laut (Cynometra ramiflora)
Katong Laut (Cynometra ramiflora) - This is the coastal tree that gives our Katong Town its name! It bears yellowish-white flowers in small clusters, and has broad-ovoid fruits which are thick and woody. This nationally critically endangered tree occurs in coastal forests and sandy beaches. The timber is sometimes used for light constructions and as firewood. Oil from the leaves and seeds is used to treat skin diseases.

4. The leaf has one to three pairs of broadly ovate or roundish leaflets.

Ipil (Intsia bijuga)
Ipil (Intsia bijuga) - This deciduous coastal/back mangrove tree is critically endangered in Singapore. The flowers occur in dense clusters, and start off white in colour before turning to dark purple eventually. The fruit is a flat pod that turns brown as it matures. It has high-end luxury wood, particularly popular for hardwood flooring but also used to produce furniture and musical instruments. The seeds are also edible. They are usually fried, soaked for a few days, then boiled and eaten. More details on this plant here.

5. The leaf has two to four pairs of narrowly ovate or heart-shaped leaflets.

Nyireh (Xylocarpus rumphii)
Nyireh (Xylocarpus rumphii) - This critically endangered tree is usually found on rocky shores or rock bunds. The flowers form hanging clusters with whitish petals, while the fruits are round, about the size of a large apple. The wood is used for making boats and wooden handicraft, such as traditional knife handles, while the bark is used for tanning and dying cloth. More details and photos here.

6. The leaf has three to seven broadly ovate leaflets, and has a terminal leaflet.

Kacang Kayu Laut (Pongamia pinnata)
Kacang Kayu Laut (Pongamia pinnata) - This common seashore tree has pinkish-white to purplish flowers and thick leathery seed pods. The bark of young trees is usually smooth, becoming shallowly fissured with age. It usually occurs on non-swampy beaches or at the landward side of mangrove forests. The oil from the seeds are used for illumination and for medicinal purposes. Recently, there were suggestions to use the oil as biofuel as well. The seeds and roots are used to make fish poison, while the bark is used to make ropes. This tree is sometimes planted along roads and coastal areas as a shade tree.

7. The leaf has two to four pairs of leaflets and winged rachis (i.e. the compound leaf stem has membrane-like extensions on both sides).

Nyamok (Guioa pleuropteris)
Nyamok (Guioa pleuropteris) - This common shrub/tree occurs in both coastal forests and inland forests. It has white flowers in simple bunches, while the fruits are three-lobed, pinkish or orange in colour. The wood is used for firewood or for making handles of axes and other small tools, or shafts for wagons.

8. The leaf has seven to nine narrowly ovate leaflets, and has a terminal leaflet.

Mangrove Trumpet (Dolichandrone spathacea)
Mangrove Trumpet (Dolichandrone spathacea) - This nationally critically endangered coast plant occurs along the landward margin of mangroves, tidal river banks and beach forest. The white trumpet-like flowers which give the plant its common name blooms at night, pollinated by hawkmoths with long tongues. The fruits are horn-shaped, and the seeds with corky wings can be dispersed by both wind and water. The bark is greyish brown, and may be fissured in old trees. The wood is light and not durable, and apart for being used as firewood, it is occasionally used to make small utensils. The leaves are sometimes used to treat mouth infections.

B) Leaf has 10 or more leaflets that are not subdivided into secondary leaflets.

9. The leaf shape is palmate with numerous leaflets radiating from the tip of the leaf stalk. Young plant has less than 10 leaflets.

Mangrove Fan Palm (Licuala spinosa) - This palm is also known as the Spiny Licuala for the numerous spines on the leaf stalk. It occurs in the more open areas of back mangroves, coastal forests and on coastal cliffs, preferring full sun. The flowers occur on branching bunches, while the fruits are small and round, turning bright orange or red as they mature. The leaves are collected by locals and weaved into food wrappers, such as the wrapper for ketupat, where rice is cooked in small squarish parcels weaved from young palm leaves.

10. The leaf has less than 50 small and short leaflets, and has a terminal leaflet.

Tongkat Ali (Eurycoma longifolia)
Tongkat Ali (Eurycoma longifolia) - This tree is often found in coastal hill forest and inland forest, and is well-known for the medicinal uses of its roots, said to improve blood circulation, increase testosterone levels and enhance sexual characteristics and performance. Studies have also shown that this plant has anti-malarial and anti-cancer properties. The flowers are small, red and occur in huge and complicated bunches, while the small fruits are reddish in colour.

11. The leaf has more than 50 leaflets, and each leaflet is less than 40cm long.

Seashore Cycad (Cycas edentata)
Seashore Cycad (Cycas edentata, previously Cycas rumphii) - This palm-like tree has between 100 to 300 leaflets on each leaf. It is nationally critically endangered, and is only found occuring naturally on Pulau Tekong, though NParks have planted many of them in various gardens and parks. There are male and female trees - the males produce cones, while the females produce leaf-like structures with numerous large spore-bearers. The small round seeds are poisonous, but can be made edible after a special treatment. The young leaves are eaten as vegetable, while the starch fro the trunk can be made into sago.

12. The leaf has more than 50 leaflets, and the leaflets near the middle are more than 50cm long. It has no obvious leaf sheath.

Coconut (Cocos nucifera)
Coconut (Cocos nucifera) - The Coconut Palm is one of the most widespread coastal plant, and is found throughout the tropics and subtropics. It is commonly found in back mangroves and sandy beaches. Young plants, like most other palms, have simple leaves instead of compound leaves. The flowers occur in branching bunches, and the fruit is covered by an outer layer of thick husk, allowing it to float well on water and get dispersed to shores far from its parent plant. It is a plant of numerous uses. The coconut meat in the fruit can be eaten, while the coconut milk squeezed from the meat can be used in curries and various cuisines. Coconut water, from the fruit, is a refreshing drink and recently studies found it to have some anti-cancer properties. Coconut oil extracted from the meat can be used for cooking. The sap derived from incising the flower clusters can be fermented and made into wine. Young leaf buds are edible, while the leaves are used for weaving into food-wrappers. The twigs from the leaves can be bundled up and made into brooms. Newly germinated coconut has a marshmallow-like substance inside which is eaten as a delicacy. The dried husk can be used for fuel and as a fire starter. The shell can be used a flower pots or as a traditional musical instrument. The stem can be used in construction. They are also planted for ornamental purposes.

13. The leaf has more than 50 leaflets and comes with a leaf sheath. There are spines along the leaf axis.

Nibong (Oncosperma tigillarium)
Nibong (Oncosperma tigillarium) - This palm occurs in clumps with several stems, usually in landward margins of mangroves (especially in the transition area with freshwater swamps) or in coastal forests. The stem is covered with spines. The flowers occur in branching bunches, while the fruits are round, turning from dark green to dark purple with maturity. This species may be confused with the similarly looking Mountain Nibong (Oncosperma horridum), which may occur in coastal forests as well, but the latter has less droopy leaflets, fewer but wider stems. The wood is hard and resistant to salt water and insect, making it useful for coastal construction, such as the poles for supporting stilt houses or kelongs, or split into strips for the flooring. It has been planted as an ornamental plant in some of our coastal parks.

C) The leaf has leaflets that are subdivided into secondary leaflets.

14. The secondary leaflets are oppositely arranged, and each leaflet has a rounded tip.

Yellow Flame (Peltophorum pterocarpum)
Yellow Flame (Peltophorum pterocarpum) - This nationally critically endangered tree has an umbrella-shaped crown and light grey bark. It has 5-11 primary leaflet pairs, which are further subdivided into another 9-20 secondary leaflet pairs. The bright yellow flowers occur in huge terminal clusters, and the seed pods are reddish brown with thin edges. It usually occurs at the back of the mangrove forests, or on sandy/rocky shores. It is commonly planted along the roadsides as a shade tree, though in the wild it is critically endangered. A yellow-brown dye can be extracted from the bark for dying batik.

15. The secondary leaflets are alternately arranged, and each leaflet has a rounded tip.

Serianthes grandiflora
Serianthes grandiflora - This nationally critically endangered tree has staked flower heads bearing yellowish white flowers. The woody seed pod is somewhat oblong-shaped. The branchlets are covered with short brown hair. It occurs in coastal forests and back mangroves.

16. The secondary leaflets are wedge-shaped, or shaped somewhat like a fishtail.

Fishtail Palm (Caryota mitis)
Fishtail Palm (Caryota mitis) - This secondary forest palm is often found at the landward margins of back mangroves or in coastal forests. It usually occurs in areas not inundated with sea water. The plant starts bearing flowers from the top of the trunk, and subsequent bunches will appear below the previous bunch near the base of a leaf stalk. The fruits are round, turning from green to dark red with maturity. The leaves and fruits contain oxalate crystals and are toxic, and may cause burns on the skin when touched. Nonetheless, some animals such as civets and hornbills are known to consume the fruits and help disperse the seeds. The fuzz from the leaves is used as a fire starter, while the sap from incising the flower stalk can be made into palm sugar or a wine. An edible starch can be extracted from the stem with care.

  • Chong, K. Y., H. T. W. Tan and 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 and L. Scholten. 2006. Mangrove guidebook for Southeast Asia. RAP Publication 2006/07. FAO Regional Office for Asia and the Pacific and Wetlands International. Bangkok. 769 pp.
  • Ng, P. K. L.and N. Sivasothi. 1999. A guide to the mangroves of Singapore 1 : the ecosystem and plant diversity. Singapore Science Centre. Singapore. 168 pp.

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