Grieving crowds have been asked to stop leaving Paddington Bear toys and wrapped marmalade sandwiches as tributes to the Queen.
Mourners have instead been advised to place only unwrapped flowers and sandwiches in Green Park as staff are struggling to cope.
The Royal Parks is also urging well-wishers to refrain from leaving balloons and lit candles due to their threat to wildlife.
The charity said on its website: "In the interests of sustainability, we ask visitors to only lay organic or compostable material."
Video shows people removing the plastic wrapping from floral tributes.
However, the Royal Parks says this means the flowers will last longer and compost quicker.
For the latest updates as the world mourns the Queen and King Charles III's reign begins, follow our live blog.
Thousands of people have descended on Buckingham Palace, Windsor Castle and Balmoral following the sudden death of the monarch on Thursday.
Her Majesty, 96, had appeared in a sketch alongside Paddington Bear as part of her Platinum Jubilee celebrations in June.
In it, she comically revealed she keeps a marmalade sandwich in her handbag - a favourite food of the fictional children's book character.
However, photos already show sandwiches people have left to mark the Queen's death turning black with mould.
Ismial Ibrahim, who manages the Cool Britannia gift shop near the Palace, told Sky News he has seen a "huge flow of people" over the last three days.
"The footfall has gone really high and since then people have started asking about anything to do with the Queen," he said.
The Royal Parks went on to encourage cards and labels being left, and added they will be eventually "separated from flowers and stored".
Its statement continued: "Unfortunately, no gifts and artefacts will be accepted, and the public will be asked not to bring these to the parks.
"Non-floral objects/artefacts such as teddy bears or balloons should not be brought."
The tributes will remain in place until after the Queen's state funeral on September 19, when they will be removed over an estimated 14 day period.
The Queen's procession arrived this afternoon in the Palace of Holyroodhouse after the long journey from her beloved Balmoral estate, with her grieving children Prince Andrew, Prince Edward and Princess Anne lining up to greet her coffin.
Crowds gathered in the city to pay their respects at the Palace, where Her Majesty's body will remain for the night.
HM's coffin, which has been draped with the yellow Royal Standard of Scotland, will rest in the throne room until tomorrow afternoon.
It will then travel in a procession to Edinburgh's St Giles' Cathedral, along the Royal Mile, with the King and the late Queen's other children the Princess Royal, the Duke of York and the Earl of Wessex following behind on foot, along with Anne's husband Admiral Sir Tim Laurence.
* This weekend, the Daily Mirror and Sunday Mirror celebrate the life of Her Majesty the Queen with a commemorative special filled with all the key moments from Britain’s longest reigning monarch.
Be sure to pick up your copy of the Daily Mirror and Sunday Mirror to get both pullouts.
