This is an ornamental plant often used for hedging that grows all over the island. It has yellow trumpet-like flowers and a fruit the size of a conker. Inside is a single large seed and one of these seeds is enough to kill you, the online edition of BBC News reported.
Although the plant grows in large parts of the tropics, it's only in Sri Lanka that it has become associated with suicide - and only fairly recently, with an incident 25 years ago.
Two girls in the northern part of the island took the seed and died.
As a result of the newspaper publicity it entered the public consciousness. "The next year," says Michael Eddleston, the British doctor who has spent much of the past 10 years in Sri Lanka, "there were 23 cases; the year after that 46, then 126, and ever since then it has continued to rise year on year as it spreads across the island."
"It completely overwhelms the health service. Often young people use it as a way of getting back at people. They get scolded and they take a yellow oleander seed.
"I remember one girl said her mother wanted her to get up and do the shopping. She said no, her mother scolded her and she took a yellow oleander seed."
Eddleston claims that there is no treatment available in Sri Lanka because it's too expensive and to treat one patient could cost around $3,000.
"Most of the time people get oleander with very small, minor reasons. I think we have to do something to reduce the rate of admission to the hospital."
Eddleston recommends a government campaign to get people to cut down their yellow oleander trees.