Shaped like a giant tree, the 21-metre-high sculpture was designed by the Thomas Heatherwick-led studio to draw attention to a tree-planting campaign to mark 70 years of the Queen's reign.
It will be officially unveiled on 2 June as part of the Queen's Platinum Jubilee weekend celebrations.
The images show the sculpture outside Buckingham Palace, which is the Queen's London residence, largely complete. The final section of the sculpture is due to be installed at the top of the tree-like form later today.
When complete the tree-like form, fabricated by UK-based Millimetre, will support 350 living trees on its steel branches, giving it the name Tree of Trees.
It has a central steel structure surrounded by stacked steel tubes that twist to form the tree's trunk and extend to form branches at the upper levels.
Supported on the branches will be 350 trees of different types found across Britain. The trees were placed in aluminium pots and will be maintained using an integrated irrigation system during the two-week installation.
Following the Jubilee celebrations, the structure will be dismantled and the trees returned to storage before being donated to community groups across the country for planting in October.
Tree of Trees was designed to draw attention to a tree-planting program called the Queen's Green Canopy, which aims to encourage tree planting to mark the Jubilee. Since October the program has seen over a million trees planted in the UK.
Founded by Heatherwick, Heatherwick Studio is a London-based architecture and design studio.
Previously the studio has integrated trees and plants into several buildings including the recently completed 1,000 Trees project in Shanghai, a plant-filled Maggie's Centre in Leeds and a skyscraper in Singapore with balconies overflowing with plants.
Previously in London, Heatherwick proposed creating a tree-covered bridge across the river Thames, which was called the Garden Bridge. Following several investigations, the project was scrapped in 2017.
The photography is by Tom Ravenscroft unless stated. Main image is by Raquel Diniz.