The King's Award recognises three decades of volunteer effort to remove invasive plants from the coast and countryside.
The Guernsey Conservation Volunteers have received the highest national honour for charities,the King’s Award for Voluntary Service.
The group is the first in the Bailiwick to earn the award since it was renamed following King Charles’ accession to the throne.
The charity was founded in the mid 1990s and since then volunteers have tackled species that threaten to take over parts of Guernsey.
Angela Salmon, who heads up the organisation, says both the sour fig and the stinking onion have taken hours of effort to knock back:
"We've removed more than 250 tonnes of sour fig over the years.
"That allowed coastal habitats to restore, and the biodiversity really increases, you get all the insects and birds, and I'm really proud of that project."
Places tackled included Les Tielles cliffs and the area between L'Eree and Rocquaine where it is believed the German Army introduced the sour fig to help camouflage bunkers.
Angela says the volunteers have also been trying to keep the numbers of stinking onions down in St Peter Port's Bluebell Wood, where the delicate native flower can be easily overwhelmed:
"Over the past four years we have probably removed half a million stinking onion bulbs in the Bluebell Wood.
"If nothing happened it would become stinking onion wood which isn't quite as appealing."
The award will be presented by Guernsey's Lieutenant Governor and two representatives from the Guernsey Conservation Volunteers will attend a garden party at Buckingham Palace next year, along with other winners.
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