Your paper (Sunday Times, October 4, 2009) highlighted the spread of alligator weed in an article titled “Beware of Alligator”.I have been working on alligator weed in Australia since 1995. This is not a native plant of Australia, but of Brazil and Argentina (it comes from the Amazon River basin).
Its presence in Australia was first recorded in 1946, when it was found growing on ballast dumped by wartime shipping.
Alligator weed is described as a noxious weed in all Australian states and territories. It is highly suited to the climates in Australia, where it has become naturalised. The weed is also found in New Zealand, the United States, China, Indonesia, Malaysia, Thailand, India and Sri Lanka.
Since the ’60s, the plant has been mistakenly grown as a vegetable by Sri Lankans living in Australia. As an invasive plants specialist, I identified the error in 1995.
Alligator weed is amphibious and can grow in a variety of habitats ranging from damp soil along the shoreline of rivers, canals, wetlands, ponds, lakes, streams and ditches, but usually in fresh-to-slightly brackish water. It can withstand some salinity. This amazing plant can grow in wet soil or in dry land without any water for several months.
The weed’s health risk has not been properly studied so far. The main problem with the plant is its ability to invade water resources such as salvinia and water hyacinth. We do not want another invasive plant choking our water resources.
Alligator weed may have came to Sri Lanka from Australia via humans and been mistakenly planted here as a vegetable.
Identifying alligator weed is easy. The flower is larger (1-3 cm wide) and grows at the end of stalks (4-9 cm long).
The mukunuwenna flowers are small (less than 5 mm) and grow in clusters at the leaf joints. But you do not see flowers during the vegetative growth stages, when people harvest these plants for sale.
The two species can be identified more easily by looking at the stems. The Alligator weed stem is soft and hollow, while the mukunuwenna stem is woody.
Learn to identify “kimbulwenna” or Alligator weed, but don’t stop eating “mukunuwenna”. It is a very healthy green.
Dr. Lalith Gunasekera,