This is an indigenous species that belongs to the Scrophulariaceae family and is found in wet lowlands up to an altitude of about 500 meters. It grows in masses, along banks of tanks, paddy fields and marshes in the dry lowlands. This species is found throughout the eastern tropics including India, Myanmar, Thailand, Malaysia, Indonesia and Vietnam.
I have observed and photographed this species in Kilinochchi in January 2010, the outer parts of the lobes of which were of a darker purple and most did not have a pale mid-lobe unlike the flowers that I have observed in Wilpattu. I have also seen this species in bloom in Mannar and at Vidaththalthivu on the Punareen road.
One of the most picturesque sights in Wilpattu is millions of these brilliant purple flowers fluttering in the breeze around a white sand rimmed villu. The flowers of this species can be observed from March to September around most villus.