Giant Cabomba (Cabomba aquatica)

Lotus Pond, Kingfisher Wetlands

“Look at those miniature pads - is it a dwarf water lily (Nymphea spp.)? No, with those single-petaled, bright yellow flowers, it’s obviously a yellow water snowflake (Nymphoides geminata)! Wait, it’s growing from a submersed plant that looks like…a Cabomba?! Who would have thought this aquatic weed could have such pretty flowers and cool floating leaves!” Such was my internal narrative when I first approached the waterfront at the Kingfisher Wetlands Wildlife Lookout a week ago. 

This week’s What’s Blooming feature plant might be one you have in your own home – if you keep a well-lit freshwater aquarium, that is! The giant cabomba (Cabomba aquatica) and its cousin, the Carolina fanwort (Cabomba caroliniana) are often sold in the aquarium trade as attractive underwater plants with their plush, finely divided pinnate leaves that sway gently in the water current. 

Hailing from ponds, lakes, and gentle streams in northern South America, from Venezuela to Brazil, this plant is fully aquatic and rooted in the underwater soil bed of the waterbodies it grows in. Its reddish stems can get up to 1.5 in length and support oppositely arranged pairs of feathery, fan-shaped leaves, so finely divided that each leaf can have up to 500 segments! 

What initially stymied me about this plant was its rounded, floating leaves, superficially resembling those of water lily (Nymphaea spp.) to which it is distantly related, but without a cleft or split. The giant cabomba, to my surprise, exhibits two distinct leaf forms – a phenomenon called heterophylly, from the Greek for ‘different’ and ‘leaf’. 

The primary leaves are the finely dissected fan-shaped aquatic leaves that are borne on opposite sides of the stems. These are the primary drivers of photosynthesis for the plant’s growth. However, when the plants are triggered to flower – reportedly year-round in parts of its native habitat in Brazil, but likely seasonally in Singapore - the growing tip of each shoot starts to develop leaves of a very different shape: simple, ovate or elliptical leaves with a solid blade with a leaf stalk attached to the centre of the underside of each leaf. These are informally called ‘floating leaves’ as the leaf blades float at the water’s surface. 

Each leaf supports a small flower about 2-3cm above the water and 1cm in diameter. The outer three bright yellow sepals and inner trio of almost-identical petals are difficult to distinguish from each other except by their relative position and are together called tepals. Each flower opens for just two days attracting insects like bees or flies to come pollinate it, after which it develops a tiny fruit with single oval seed that is released underwater. 

Find the giant cabomba displaying both its feathery submerged and rounded floating leaves as well as its bright yellow flowers in Lotus Pond at the Kingfisher Wetlands Wildlife lookout! Come in the morning, as the flowers close in the late afternoon.

This article is part of our What's Blooming series.