22 July 2017

Favourite Nectaring Plants #11

Butterflies' Favourite Nectaring Plants #11
The Buas-Buas / Malbau (Premna serratifolia)

A Common Rose feeds on the flower of the Buas-Buas

In this 11th article of Butterflies' Nectaring Plants series, we feature a medium-sized tree that can grow up to at least 7-9m tall, the Buas-Buas / Malbau (Prema serratifolia). This plant is a native to Southeast Asia, including Singapore, but ranges from East Africa all the way to Australia and the Pacific Islands. The plant has a preference for terrestrial (Coastal Forest), shoreline (Mangrove Forest; Sandy Beach) habitats and can thrive in harsh environments near the sea. It grows along rocky and sandy coasts, in open country, near mangroves and other coastal sites.

A large Buas-Buas bush spreading extensively

The Malbau (locals in Southeast Asia call it Buas-Buas), is a spreading, evergreen multi-branched shrub or small tree with a low crown, with woody trunks when mature. It has green to brown bark which is smooth or scaly. The Malbau has the distinction of being named by the prominent Swedish botanist and 'father of taxonomy' Carl von Linnaeus in 1771.

In Singapore, Buas-Buas can be found in open wastelands, coastal reclaimed sand-filled sites, offshore islands like Semakau, Ubin, Hantu, St John's and Sisters Islands and even at the fringes of our nature reserves. As the plant is considered common and easy to propagate, either by seeds or cuttings, it has begun to find its way into community gardens, butterfly gardens and roadside planting as a butterfly nectaring plant. The Buas-Buas can also be found in the Healing Garden at the Singapore Botanic Gardens, where there are occasionally many visiting butterflies at the flowers of the plant.

A pristine bush of the Buas-Buas

Plant Biodata :
Family : Lamiaceae (Labiatae)
Genus : Premna
Species : serratifolia
Synonyms : Premna foetida, Premna obtusifolia var. serratifolia, Premna borneensis, Premna kunstleri
Country/Region of Origin : Eastern Africa, across the Indian Ocean and through tropical Asia to Australia and the Pacific Islands
English Common Names : Malbau, Bastard Guelder
Other Local Names : Buas-Buas, Bangkung Kayu, Sarunai, Singkel, Arani, 伞序臭黄荆

Close-ups of the Buas-Buas leaves - young leaves are glossy and light green

The leaves of the Buas-Buas are opposite, range between 5 to 18 cm long, 3 to 10 cm wide, broadly ovate with a smooth leathery texture. The simple, stalked leaves have leaf blades that are elliptical, glossy dark green above, light green below with prominent veins and the midrib raised on the underside of the leaf. The leaf margins are smooth (or rarely serrated) and hairless, and the crushed leaves apparently smell of cat's urine. The stems on which the leaves are borne are smooth and green when young, turning woody towards the base of an older plant.

Flower buds of the Buas-Buas where the white flowers have yet to bloom

A close up of the white flowers of the Buas-Buas

The numerous flowers are cream-green in colour, with rather an unpleasant odour, borne on spreading terminal panicles about 10–20 cm across. Its greenish-white or white flowers are 2.5 mm wide, and arranged in clusters that are 5–13 cm wide. The white flowers have five corolla lobes. It is interesting to note that despite the flowers' pungent and foetid odour, it may be this smell that attracts a variety of butterflies to feed on the flowers.

Fruits of the Buas-Buas.  Note the black/dark purple ripened berries

The fruits are more or less spherical, 3-8 mm long, 3-5 mm wide and hairless. They are green initially but turn black or dark purple when ripened. There is a single seed in the fruit. As the plant flowers all year round, the ripened fruits may be collected for easy propagation of the plant. The fruits can be found in clusters and are eaten by birds, which probably aid in the natural distribution of the Buas-Buas. The fruits and seeds can apparently be eaten by humans too.

The Buas-Buas has a variety of medicinal uses. The leaves and roots are used in traditional medicine as a diuretic and to treat rheumatic arthritis; colic and flatulence; coughs, headaches and fevers In various parts of Indonesia, an infusion of the leaves and roots is used against fevers and shortness of breath; women also eat the leaves in order to promote breast-milk production. In Australia, aborigines used this plant to treat the stings of stonefish and stingray, as well as spear wounds. Juice squeezed from the berries is used as nose drops to treat sinus headaches. Research is in progress on extracts from the bark and wood that contain alkaloids and iridoid glycoside, as these are believed to prevent cardiovascular disease.

Two Leopards feeding on the flowers of the Buas-Buas

The small pungent white flowers are attractive to butterflies. Due to the size of the flowers and probably the small amount of nectar, butterflies that feed on the flowers move very quickly from flower to flower and stopping for fleeting moments only. This makes photographing the feeding butterflies more challenging compared to those that feed for longer periods on other nectaring plants.

A variety of the fast-flying and larger Swallowtail butterflies (Papilionidae) feeding on the Buas- Buas flowers

Interestingly, despite the size of the flowers, we have seen many of the larger Papilionidae feeding on the flowers of the Buas-Buas. Even the large Common Birdwing (Troides helena cerberus) has been photographed fluttering and feeding on the flowers of the plant. Amongst the strong flyers, the Common and Lesser Jays, Tailed Jay, Common Bluebottle, Common Rose, Lime Butterfly and Common Mormon have been observed visiting the flowers of the Buas-Buas.

Some Danainae of the flowers of the Buas-Buas

Amongst the Danainae, the large Crows like the Spotted Black, Striped Blue and the King Crow have been seen amongst the flowers of the plant. On Pulau Ubin, where the Dwarf Crow has been reliably and regularly seen, it also feeds on the flowers of the Buas-Buas. The various Tigers also occasionally stop to visit the flowers of the plant for their nutrition.

Striped Albatross and Lemon Emigrants feeding on the Buas-Buas flowers

The larger Pieridae also seem to like the flowers and we have seen the Striped Albatross and Emigrants feeding. The Grass Yellows also flutter amongst the Buas-Buas, but I have not seen a confirmed shot of any of them feeding on the flowers yet, though I am quite sure that they would.

A variety of Nymphalidae butterflies feeding on the Buas-Buas flowers

Other species of the Nymphalidae also feed on the flowers of the plant, and the skittish Leopard, Rustic, Chocolate/Blue/Peacock Pansy and Malayan Eggfly have been observed at the flowers. Even the Ypthima have been spotted at the flower of the Buas-Buas, and there is a also particular bush near Lower Peirce Reservoir Park that is often popular with the Malayan Five Ring.

A Chestnut Bob feeding on a Buas-Buas flower

Some Hesperiidae have also been spotted on the Buas-Buas flowers, and there are likely to be many more that have been missed. A confirmed sighting of a Chestnut Bob feeding on the flowers suggests that other skippers may also find the nectar of this plant's flowers attractive.

Wasps and day-flying moths also enjoy the flowers of the Buas-Buas

Besides butterflies, the Buas-Buas flowers also attract a variety of other flying insects, from day-flying moths to bees and wasps. However, it is curious that at times, the flowers of the plant are totally devoid of any pollinating insects in certain locations. Could it be because there are other, more preferable nectaring sources, or the location of the plant in a particular habitat renders it unattractive to insects due to insufficient production of nectar?

When you are out butterflying, do look out for the Buas-Buas, which usually flowers quite prolifically all year round when the shrub matures. Keep track of the number of species of butterflies that feed on the flowers and send in your feedback on this post.

Text by Khew SK : Photos by Ang Wee Foong, Bob Cheong, Huang CJ and Khew SK

Butterflies' Favourite Nectaring Plants #10 : Mile-A-Minute

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