An employee decorates a Christmas tree with a coronavirus-shaped bauble ahead of the New Year and Christmas season at a botanical garden in the settlement of Nikita, Crimea December 29, 2021. REUTERS/Alexey Pavlishak 

British Secretary of State for Health Matt Hancock, with G7 health ministers, takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

A plaque at a memorial tree planting site at Oxford Botanic Gardens is seen, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health Matt Hancock and U.S. Secretary of the Department of Health Xavier Becerra , with G7 health ministers, attend a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

U.S. Secretary of the Department of Health Xavier Becerra takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

EU Secretary of State for Health, Stella Kyriakides, with G7 health ministers, attends a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock, his EU counterpart Stella Kyriakides, and U.S. Secretary of the Department of Health Xavier Becerra take part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock, with G7 health ministers, takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health Matt Hancock with Oxford University Hosptials NHS Foundation Trust's Chief Nursing Officer Sam Foster takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health Matt Hancock with his EU counterpart, Stella Kyriakides attends a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health Matt Hancock and U.S. Secretary of the Department of Health Xavier Becerra, with G7 health ministers attend a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

Oxford University Hosptials NHS Foundation Trust's Chief Nursing Officer Sam Foster takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

U.S. Secretary of the Department of Health Xavier Becerra, with G7 health ministers attends a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock speaks at a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock, with G7 health ministers, takes part in a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock speaks at a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock speaks at a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

British Secretary of State for Health, Matt Hancock speaks at a memorial tree planting ceremony at Oxford Botanic Gardens, following a G7 health ministers meeting, ahead of the G7 leaders' summit, at Mansfield College, Oxford University in Oxford, Britain June 4, 2021. Steve Parsons/PA Wire/Pool via REUTERS 

Women wearing protective face masks walk past blossoming lilac trees as they visit a botanical garden in Kyiv, Ukraine May 23, 2021. REUTERS/Valentyn Ogirenko 

People visit RoozenGaarde display garden during the Skagit Valley Tulip Festival, which was canceled last year due to the coronavirus disease (COVID-19) outbreak, in Mount Vernon, Washington, U.S., April 23, 2021. Picture taken April 23, 2021. REUTERS/Lindsey Wasson 

A visitor uses her mobile phone while looking at a tulip patch at Descanso Gardens in La Canada Flintridge, California, U.S., April 7, 2021. REUTERS/Mario Anzuoni 

Visitors sit by a tulip patch at Descanso Gardens in La Canada Flintridge, California, U.S., April 7, 2021. REUTERS/Mario Anzuoni 

A visitor uses her mobile phone while looking at a tulip patch at Descanso Gardens in La Canada Flintridge, California, U.S., April 7, 2021. REUTERS/Mario Anzuoni 

Visitors walk by a tulip patch at Descanso Gardens in La Canada Flintridge, California, U.S., April 7, 2021. REUTERS/Mario Anzuoni 

Visitors use their mobile devices as they look at a tulip patch at Descanso Gardens in La Canada Flintridge, California, U.S., April 7, 2021. REUTERS/Mario Anzuoni 

Visitors pose and take pictures among the 50 acres of Ranunculus flowers at "The Flower Fields" in Carlsbad, California, U.S., March 31, 2021. Picture taken March 31, 2021. REUTERS/Mike Blake 

Customers browse plants at Lydstep Nurseries and garden centre, as coronavirus disease (COVID-19) restrictions in Wales begin to ease, in Lydstep, Britain March 22, 2021. REUTERS/Rebecca Naden REFILE - CORRECTING YEAR 

Kew horticulturalist Joanna Bates tends to a 'Yellow Hearts to Remember' planting tribute to remember those lost to COVID-19, a year since the first British lockdown began due to the coronavirus disease pandemic, Royal Botanic Gardens, Kew, London, Britain, March 22, 2021. REUTERS/Toby Melville 

Kew horticulturalist Joanna Bates tends to a 'Yellow Hearts to Remember' planting tribute to remember those lost to COVID-19, a year since the first British lockdown began due to the coronavirus disease pandemic, Royal Botanic Gardens, Kew, London, Britain, March 22, 2021. REUTERS/Toby Melville 

Kew horticulturalist Joanna Bates tends to a 'Yellow Hearts to Remember' planting tribute to remember those lost to COVID-19, a year since the first British lockdown began due to the coronavirus disease pandemic, Royal Botanic Gardens, Kew, London, Britain, March 22, 2021. REUTERS/Toby Melville 

Kew horticulturalist Joanna Bates tends to a 'Yellow Hearts to Remember' planting tribute to remember those lost to COVID-19, a year since the first British lockdown began due to the coronavirus disease pandemic, Royal Botanic Gardens, Kew, London, Britain, March 22, 2021. REUTERS/Toby Melville 

Kew horticulturalist Joanna Bates tends to a 'Yellow Hearts to Remember' planting tribute to remember those lost to COVID-19, a year since the first British lockdown began due to the coronavirus disease pandemic, Royal Botanic Gardens, Kew, London, Britain, March 22, 2021. REUTERS/Toby Melville 

A tourist rides a bicycle at the Tropical Botanical Gardens in Xishuangbanna Prefecture, Yunnan province, China, January 26, 2021. Picture taken January 26, 2021. REUTERS/David Stanway 

A woman wearing a protective face mask amid the outbreak of the coronavirus disease (COVID-19) walks in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

People wearing protective face masks amid the outbreak of the coronavirus disease (COVID-19) walk in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

A woman wearing a protective face mask amid the outbreak of the coronavirus disease (COVID-19) walks in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

A woman wearing a protective face mask amid the outbreak of the coronavirus disease (COVID-19) sniffs a flower in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

People wearing protective face masks amid the outbreak of the coronavirus disease (COVID-19) walk in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

A man wearing a protective face mask amid the outbreak of the coronavirus disease (COVID-19) walks in a botanical garden in the settlement of Nikita, Crimea October 29, 2020. REUTERS/Alexey Pavlishak 

A woman dressed as angel wears an illuminated face mask ahead of a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A man dressed as Santa Claus and woman dressed as angel wear face masks as they leave a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A man dressed as Santa Claus and woman dressed as angel wear face masks as they leave a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A man dressed as Santa Claus and woman dressed as angel wear face masks ahead of a news conference to introduce the upcoming Christmas Garden event of iluminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A man dressed as Santa Claus and woman dressed as an angel leave a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A man dressed as Santa Claus and woman dressed as angel wear face masks ahead of a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

A woman dressed as angel wears a face mask ahead of a news conference to introduce the upcoming Christmas Garden event of illuminated objects at a botanic garden, amid the coronavirus disease (COVID-19) outbreak, in Berlin, Germany, October 8, 2020. REUTERS/Fabrizio Bensch 

People enjoy the sun at Royal Botanic Garden Sydney as the state of New South Wales continues to report relatively low numbers for new daily cases of the coronavirus disease (COVID-19), in Sydney, Australia, September 7, 2020. REUTERS/Loren Elliott 

A Javanese lesser adjutant is seen at a confinement area as a zookeeper cleans it at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam, August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

Camels eat at their confinement area at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A zoo worker prepares food after receiving food donations at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A zoo staff member prepares food donated to Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

Mahouts wearing protective masks bathe an elephant at a confinement area at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

Bananas donated by zoo lovers are seen after a public community call for food donations for Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

Nguyen Phuoc Thinh, a veterinarian in charge of caring for illegally smuggled rescued animals, weighs a rare turtle confiscated by the police, at Saigon Zoo and Botanical Gardens which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19) in Ho Chi Minh, Vietnam, August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A mahout stands between elephants at their confinement area at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A mahout wearing a protective mask walks between elephants at their confinement area at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A giraffe walks at her cage next to an empty restaurant at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam, August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

Mahouts wearing protective masks gather beside an elephant at a confinement area at Saigon Zoo and Botanical Gardens, which is facing dwindling visitor numbers due to the coronavirus disease (COVID-19), in Ho Chi Minh, Vietnam, August 19, 2020. Picture taken August 19, 2020. REUTERS/Yen Duong 

A couple takes video at the Bellagio Conservatory & Botanical Gardens during the reopening of Bellagio hotel-casino, closed since March 16, 2020 as part of steps to slow the spread of the coronavirus disease (COVID-19), in Las Vegas, Nevada, U.S., June 4, 2020. REUTERS/Steve Marcus 

Guests look over the "Japanese Spring" display in the Bellagio Conservatory & Botanical Gardens during the reopening of Bellagio hotel-casino, closed since March 16, 2020 as part of steps to slow the spread of the coronavirus disease (COVID-19), in Las Vegas, Nevada, U.S., June 4, 2020. REUTERS/Steve Marcus