Heatherwick Studio has released images of its completed Tree of Trees sculpture outside Buckingham Palace in London, which formed part of the Queen's Platinum Jubilee celebrations.

Supporting 350 small trees on a steel structure, the tree-like form was illuminated on 2 June as the first in a chain of 1,500 beacons lit across the UK and Commonwealth countries for last weekend's Platinum Jubilee celebrations.

Standing outside Buckingham Palace, which is the Queen's London residence, the 21-metre-high sculpture was designed to draw attention to the Queen's Green Canopy tree-planting campaign.

Since October, the program has seen over a million trees planted in the UK to mark 70 years of the Queen's reign.

"The job was to create a communication device to emphasise an initiative," explained Heatherwick Studio founder Thomas Heatherwick. "It's deliberately creating a focal moment."

"If we brought a normal tree, no one's going look at it because they normally look at trees. So you have to do something extraordinary," he told Dezeen.

"Otherwise, it wouldn't do the job. So we would be failing as designers if we didn't do something that captures people's engagement, and provokes questions."

The temporary sculpture, which will stand for two weeks, contains 350 trees of different types found across Britain. They are held within aluminium pots supported on reclaimed steel branches, fabricated and assembled by UK-based maker Millimetre.

"We were asked by the Queen's team to make a project that drew attention to her amazing initiative," said Heatherwick.

"We only had a week to design it. It's one of those things where you're moving faster and thinking on your feet, working with an amazing team of engineers, arborists, fabricators and nurseries and all the different things," Heatherwick added.

Heatherwick Studio aimed to design a form that was clearly tree-shaped but was not simply a replication of a tree.

"Our thought was that we would highlight the planting side, but they are planting small trees, so if we placed one of those here, it'd be totally insignificant," he continued.

"If we brought a full-sized tree, it would blend in because we're next to Green Park. So we needed to do something that was unfamiliar and drew the eye. It's like creating a tree without simulating exactly a tree."

The sculpture was criticised in the UK, with some comparing it to mobile telecommunication masts that are sometimes disguised as trees and Guardian critic Oliver Wainwright likening it to the controversial Marble Arch Mound.

"[It is] another example of the recent fetish among certain architects and designers for conjuring a cartoonish version of nature, suspending shrubbery and balancing trees in ways that make the plants look decidedly unhappy to be there," wrote Wainwright.

Others, including Dezeen commenters, asked if planting a tree would be a better way to promote a tree-planting campaign.

"In a sense, that's a good question," said Heatherwick when asked about this. "Because, in a sense, planting trees is a banal thing – yet trees are simultaneously the superheroes of our towns and cities."

"We've learned more than ever, that biodiversity isn't just a nice thing, it's essential for our mental health," he continued.

"We know the benefits of nature within cities – reductions in crime and antisocial behaviour, the reduction in time for people to get to heal are significantly improved by proximity to trees and nature. So how do you draw attention to something we all already know already? You give it a twist?"

The structure is set to be dismantled within the next two weeks with the trees relocated to a nursery in Cambridgeshire before being sent to community groups across the country for planting in October.

Founded by Heatherwick, Heatherwick Studio is a London-based architecture and design studio that has previously integrated trees and plants into buildings including the recently completed 1,000 Trees project in Shanghai and a skyscraper in Singapore.

The photography is by Jonathan Banks unless stated.