March 2010: Ipomoea aquatica, water spinach

Botany

March, 2010: Ipomoea aquatica, water spinach

A popular Asian vegetable that can become a serious aquatic weed.

Ipomoea aquatica, water spinach
Photograph courtesy of Shirley Denton, Atlas of Florida Vascular Plants

Family: Convolvulaceae, the Morning Glory family

Distinguishing Characteristics: This is a herbaceous, trailing vine with milky sap and hollow stems that can reach 10 feet in length; the stems produce roots at the nodes and float in aquatic habitats. The leaves are simple and alternate, usually slender and arrowhead shaped but they vary to triangular or cordate; they have long petioles, and the blades range from 2 to 7 inches long. The flowers are trumpet-shaped, like those of morning glories, white or pale lavender, and about 2 inches across; they are borne singly or few together in the axils of the leaves. The capsules are spherical, woody at maturity, and about ½ inch in diameter.

Ipomoea aquatica, water spinach
Photograph courtesy of Shirley Denton, Atlas of Florida Vascular Plants

Distribution: This plant is native to China, but it is widely naturalized in tropical and subtropical areas around the world. In the United States, it has been reported from Hawaii, California, Florida and Puerto Rico.

Occurrence in Florida: At present, water spinach is established in ditches, canals and a few natural lakes in Pinellas, Hillsborough, and Manatee counties, but escapes from cultivation have been found in scattered localities throughout the state. It also grows terrestrially on the banks of streams and canals.

Similar Species in Florida: Twenty-four other species of Ipomoea are native or naturalized in Florida. This species is unique in its hollow stems, its stems producing roots at the nodes, its milky sap, and its aquatic habitat. Water spinach is particularly similar to the sweet potato (Ipomoea batatas), especially when growing terrestrially, but the two plants can easily be separated by the characters enumerated above.

Ipomoea aquatica, water spinach
Photo by Forest & Kim Starr, Hawaiian Ecosystems at Risk project (HEAR)

Means of Dispersal: Mature plants can produce hundreds of seeds annually, and these are readily dispersed by water. In addition, stem fragments are hollow and can float for long distances, starting new colonies when they come to rest.

Comments: This plant forms dense, floating mats of intertwined stems in slow-moving water, impeding boat traffic and shading or choking out native aquatics. It is a serious weed in the Philippines and other tropical countries, and it must be carefully monitored to prevent it from becoming one in the United States. Water spinach is on the federal noxious weed list and is classified as a Class I Prohibited Aquatic by the State of Florida. However, registered nurseries are allowed to grow it for sale outside of Florida, under a compliance agreement with DPI. These nurseries must follow stringent guidelines and they are subject to quarterly inspections. The plant is a nutritious vegetable and is popular among people of Asian ancestry. It is often sold illegally in their markets.

Further Information: Langeland, K.L., H.M. Cherry, C.M. McCormick, and K.A. Craddock Burks. 2008. Nonnative plants in Florida's natural areas. IFAS Communication Services, University of Florida, Gainesville. 193 pp. (DPI library).

Dr. Richard Weaver, Botanist
Florida Department of Agriculture and Consumer Services
Division of Plant Industry
1911 SW 34 St.
Gainesville, FL 32614-1201