The Imperial Networks of the Water Hyacinth (Pontederia crassipes) in Southeast Asia

Water hyacinth (Pontederia crassipes), a plant native to South America, is a ubiquitous weed throughout Southeast Asia. It was cultivated in ponds at the Buitenzorg Botanic Gardens beginning in 1894 for its horticultural value. This free-floating perennial aquatic plant grew at an expeditious rate, particularly in water containing high concentrations of sewage. It quickly moved through Southeast Asian botanic networks as a planned introduction to provide aesthetic beauty to water systems but also to counter algae blooms, provide animal feed and act as compost, or biochar. By 1901 Thai royalty brought a sample to Bangkok, from where it spread throughout the Chao Phraya delta, and eventually to Cambodia and the Mekong River, causing concern as early as 1908. The plant arrived in the Philippines by 1912. In each instance it was too successful, usually outcompeting native flora and reducing oxygen in the water, thus reducing the biodiversity of flora and fauna in ecosystems where it came to dominate. This paper will discuss how the introduction of this seemingly innocuous plant reflects the role and power of empires, botanical networks and histories in the transforming ecology of imperial pasts in Southeast Asia, a legacy that remains well into the 21^st century.