ORIGIN

Mexico to Argentina

COMMON NAME

Senegal tea

BOTANICAL NAME

Gymnocoronis spilanthoides

IDENTIFICATION

Senegal tea is a perennial, semi-aquatic herb, growing to 1.5 metres when flowering.

Stems are usually 5 to 10mm in diameter when young, increasing up to 20mm with age. Young stems are often angled, with several ridges running down the length of the stem, but they become more or less rounded as they mature. Stems normally scramble, branch and root at the nodes, forming an intertwining mat. Larger stems are hollow between the nodes and mats are buoyant in water. Erect stems are produced prior to flowering, growing to a height of 1.5m or more.

HABITATS

It is restricted to wet marshy soils and still or flowing water, where it can grow as a floating mat extending from the margins of the waterbody.

IMPACT TO BIOTA AND ECOSYSTEMS

Senegal tea is an extremely hardy plant and once established at a site it is difficult to control. In fertile situations its growth rate can exceed 150mm a week. It forms dense floating mats which can quickly cover waterbodies, excluding other life forms as well as impeding water flow, navigation and recreational activities. Problems with flooding due to impedance by this plant have already occurred in New Zealand.

DISPERSAL ROUTES, VECTORS, INFESTATION SOURCES

Senegal tea can spread by vegetative fragmentation, new plants produced from the stem nodes, or by seed. Stem fragments may be spread by water movement, deliberate plantings or by drainage machinery.

Fragments quickly develop roots and new stems when they come to rest, forming new colonies. Dispersal of seed is by water movement, or mud sticking to animals or machinery.

MANAGEMENT

Physical Control
Small infestations can be cleared by hand, ensuring that all parts of the plant, including the roots, are removed and incinerated or buried deeply. Attempts to clear sites mechanically should be carried out with caution in order not to spread fragments of the plant down stream or to contaminate machinery.

Disposal
Bury deeply underground away from watercourses.

Chemical Control
Glyphosate herbicide (mixed at the rate of 2 litres/100 litres water plus Penetrant) provides good control, however the timing of application appears critical eg spring is the best time for control.

Biological Control

Recommended Approach

FURTHER COMMENT

This plant is prohibited for sale and distribution within New Zealand.

For further information on Senegal tea please refer to Environment Bay of Plenty's Fact Sheet pp1300-Aquatic Pest Plants