WASHINGTON - United States President Barack Obama and his wife Michelle now have a Singapore-grown orchid named after them.

The Dendrobium Barack and Michelle Obama was unveiled by Prime Minister Lee Hsien Loong at the White House state dinner in their honour on Tuesday night (Wednesday morning, Singapore time).

"To mark the 50th anniversary of our relations, Singapore has named an orchid hybrid in honour of President and Mrs Obama," PM Lee said.

The toast to the presidential couple came with a quip about the conspiracy theories in the US that claim President Obama was actually born in Kenya.

"This is a hybrid of breeds native to Singapore and Hawaii, where the President was born, most of us believe," said PM Lee to laughter from the dinner guests, who included prominent US politicians and members of the Singapore delegation.

Dendrobium Barack and Michelle Obama is a cross between two hybrids: the Hawaiian Dendrobium Pink Lips and Singapore's Dendrobium Sunplaza Park. Each spray bears just over a dozen yellow blooms with purple lips.

The National Parks Board described the new hybrid as a "vigorous and free flowering" bloom.