Could it be a Brownlowia? The description from Giesen seems to fit, especially the description and drawing for Brownlowia tersa: "A shrub 1.5-2 m tall. Leaves narrow, lanceolate to elliptic-lanceolate, rigid and thin or leathery, 2-5 by 6-20 cm, with a rounded base and a pointed tip. The upper surface is glossy and smooth, while the lower surface is grey-green and covered with a dense layer of tiny, hairy scales. "The flower heads occur in axils or at the ends of branches, few-flowered, and are up to 4 cm long. The calyx is bell-shaped and 5 mm long, with 3-5 lobes. The corolla is pink with a yellow base, slightly longer than the calyx (about 6 mm), with 5 petals." In addition, Hsuan Keng mentions that the leaves are spirally alternate.
I didn't see any fruits but these are said to be "a woody capsule or nut, 15 mm long, bilobed or heart-shaped (alternatively: shaped like a golf putting-club), and is pale greyish-green, covered with small, brown warts."
There are two species of Brownlowia recorded for Singapore. According to Hsuan Keng, Brownlowia argentata grows on brackish tidal sandy soil and is rare, and was recorded at Kranji. While Brownlowia tersa grows in mangroves and was recorded for Kranji and Sungei Mandai.
According to the Red Data Book, Brownlowia argentata is considered 'Presumed Nationally Extinct' while Brownlowia tersa is 'Endangered'.
Of course it could be something else entirely. Will need expert help to sort this out!
- Hsuan Keng, S.C. Chin and H. T. W. Tan. 1990, The Concise Flora of Singapore: Gymnosperms and Dicotyledons. Singapore University Press. 222 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.
- Giesen, Wim and Stephan Wulffraat, Max Zieren and Liesbeth Scholten. 2006. Mangrove Guidebook for Southeast Asia (PDF online downloadable). RAP publication 2006/07 Food and Agriculture Organization of the United Nations Regional Office for Asia and the Pacific Bangkok.