Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT TPX IMAGES OF THE DAY) 

Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

Aerial view of fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT) 

A visitor sits among tulips at the Keukenhof park also known as the Garden of Europe, in Lisse, The Netherlands April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY) 

A tourist takes pictures of tulips at the Keukenhof park, also known as the Garden of Europe, in Lisse, the Netherlands April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY) 

A tourist takes pictures of tulips at the Keukenhof park, also known as the Garden of Europe, in Lisse, the Netherlands April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY) 

A visitor sits next to tulips at the Keukenhof park also known as the Garden of Europe, in Lisse, the Netherlands April 9, 2014. Keukenhof, employing some 30 gardeners, is considered as the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY) 

Visitors take photos of tulips at the Keukenhof park, also known as the Garden of Europe, in Lisse, the Netherlands April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. REUTERS/Yves Herman (NETHERLANDS - Tags: SOCIETY ENVIRONMENT)