The world's biggest tulip garden opened to the public on Thursday for its 75th edition, with hundreds of thousands of people expected to enjoy a bewildering array of seven million bulbs in the western Dutch city of Lisse.

Keukenhof park, southwest of Amsterdam in the heart of "bulb country", contains millions of tulips of every colour as well as other flowers across 32 hectares (80 acres).

The park is a popular tourist attraction -- 1.4 million visited last year -- that claims to be one of the most photographed spots in the world.

"This is my first time here and I'm so excited to witness the 75th anniversary," said Rocelle Brewer, 41.

She had bought a flowing pink dress embroidered with flowers specifically for the occasion.

"It's really cool here. I love the way the air smells," added Cam Upton, a first time visitor from Colorado.

Nisha Kasiliya-Ravindran, a 37-year-old from India, said she was "a bit disappointed" because many of the tulips have yet to flower completely.

"We are hoping to go to the bulb fields outside as well to hopefully see some tulips," she told AFP.

Keukenhof dates back to 1949 when a group of bulb exporters and growers inaugurated it as a showcase for their wares. 

As well as tourists from more than 100 countries, it has proved a draw for royalty, with kings and queens from several European nations attending the gala opening down the years.

This year, one of the many highlights of the show include a golden yellow tulip, named after King Charles III, and a musical extravaganza to celebrate 75 years of Keukenhof featuring Dutch opera singer Laetitia Gerards.

But the opening was also not without some controversy.

Outside the entrance gates, seven naked protesters of the climate group Extinction Rebellion briefly staged a protest against the use of pesticides in the bulb-growing industry.

"Those beautifully coloured fields hide the enormous damage caused by bulb cultivation. Insects, birds and plants die en masse due to agricultural poisons," spokeswoman Lydia Steutel said in a statement.

Most visitors however, said they were just enjoying the outdoor flower garden.

"We went around and were like playful kids, like 'oh look at this flower, oh the bridge' and just looking around," said Esther Brandt, 37, from Cologne.

The park is open this year until May 12.