EPOW - Ecology Picture of the Week

Dodder (Cuscuta sp.) parasite on Grey Mangrove (Avicennia marina),
Mai Po Wetlands, Hong Kong

Explanation:  This week we are in the Mai Po Wetlands along the Sunjen River in the extreme northwest corner of immense Hong Kong.  These wetlands are some of the last remaining native mangrove forests in the greater Hong Kong urban area, and are internationally recognized as a Ramsar wetlands site.

Native mangroves of Mai Po Wetlands, Hong Kong.

At least four species of mangrove are found here, Grey Mangrove (Avicennia marina), Many-Petalled Mangrove (Bruguiera gymnorrhiza), Brown Mangrove (Aegiceras corniculatum), and Prickly Mangrove (Acanthus ilicifolius).  But twining its way on at least the Grey Mangrove is an undesirable parasitic plant called Dodder (Cuscuta sp.).

Dodder was previously known as a member of the Morning-Glory Family (Convolvulaceae) but more recently has been put into its own family (Cuscutaceae).  The many species of Dodder are parasites on numerous native plants throughout the world, although this was the first time I had seen it on mangrove.  As it grows, Dodder entwines and can encase free-living plants, absorbing water and nutrients from its host.  

Dodder can be virtually impossible to eliminate once it spreads.  Globally widespread, Dodder is known in North America as a weed or noxious species.  It is not known if its presence on mangroves in the Mai Po Wetlands as yet poses a severe threat to native plants there.

On the other hand, some species of Dodder are said to have therapeutic value.  The plant can be boiled in water with ginger and allspice and the liquid is said to treat urinary, kidney, spleen, liver, and other infections and can act as a laxative.