A bee covered with pollen hooks itself onto a petal of a bluebell in a garden, as the spread of the coronavirus disease (COVID-19) continues, in West London, Britain, April 23, 2020. REUTERS/Toby Melville

A bee covered with pollen hooks itself onto a petal of a bluebell in a garden, as the spread of the coronavirus disease (COVID-19) continues, in West London, Britain, April 23, 2020. REUTERS/Toby Melville

A bee lands on a bluebell in a garden, as the spread of the coronavirus disease (COVID-19) continues, in West London, Britain, April 23, 2020. REUTERS/Toby Melville

A direction sign is pictured by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

A person is seen by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

A woman with a bicycle is seen by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville TPX IMAGES OF THE DAY

A direction sign is pictured as people are seen walking by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

Bluebells are pictured in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

A direction sign is pictured as people are seen walking by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

People are seen walking between bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

A man is seen wearing a protective face mask on a bicycle by bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

People are seen walking between bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

Two people wearing protective face masks are seen with bicycles between bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

Two people wearing protective face masks are seen with bicycles between bluebells in Epping Forest, Wanstead, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville

Two people wearing protective face masks walking between bluebells in Epping Forest, Wanstead as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 18, 2020. REUTERS/Toby Melville, London, Britain, April 18, 2020. REUTERS/Toby Melville

Bluebells are seen in Blackwater Wood, as the spread of the coronavirus disease (COVID-19) continues, St Albans, Britain, April 16, 2020. REUTERS/Paul Childs

Bluebells are seen in Blackwater Wood, as the spread of the coronavirus disease (COVID-19) continues, St Albans, Britain, April 16, 2020. REUTERS/Paul Childs

Bluebells are seen in Blackwater Wood, as the spread of the coronavirus disease (COVID-19) continues, St Albans, Britain, April 16, 2020. REUTERS/Paul Childs

Bluebells are seen in Blackwater Wood, as the spread of the coronavirus disease (COVID-19) continues, St Albans, Britain, April 16, 2020. REUTERS/Paul Childs

Bluebells are seen in Blackwater Wood, as the spread of the coronavirus disease (COVID-19) continues, St Albans, Britain, April 16, 2020. REUTERS/Paul Childs

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman TPX IMAGES OF THE DAY

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April turning the forest blue as they form a carpet, are pictured in the Hallerbos, also known as the "Blue Forest", that had to be closed to groups of tourists this year due to the coronavirus disease (COVID-19) outbreak, near Halle, Belgium April 13, 2020. REUTERS/Yves Herman

An Atlantic Puffin is seen amongst the bluebells on Skomer Island, Pembrokeshire, Wales, Britain May 21, 2019. Picture taken May 21, 2019. REUTERS/Rebecca Naden

An Atlantic Puffin is seen amongst the bluebells on Skomer Island, Pembrokeshire, Wales, Britain May 21, 2019. Picture taken May 21, 2019. REUTERS/Rebecca Naden

An Atlantic Puffin is seen amongst the bluebells on Skomer Island, Pembrokeshire, Wales, Britain May 21, 2019. Picture taken May 21, 2019. REUTERS/Rebecca Naden

Atlantic Puffins amongst the bluebells on Skomer Island, Pembrokeshire, Wales, Britain May 21, 2019. Picture taken May 21, 2019. REUTERS/Rebecca Naden

People ride bikes near wild bluebells, which bloom around mid-April, turning the forest floor blue, forming a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman TPX IMAGES OF THE DAY

A close-up view of wild bluebells, which bloom around mid-April, turning the forest floor blue, forming a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

People ride bikes near wild bluebells, which bloom around mid-April, turning the forest floor blue, forming a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest floor blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near Halle, Belgium April 18, 2019. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman TPX IMAGES OF THE DAY

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman

Wild bluebells, which bloom around mid-April, turning the forest completely blue, form a carpet in the Hallerbos, also known as the 'Blue Forest', near the Belgian city of Halle, Belgium April 20, 2018. REUTERS/Yves Herman