From hidden rules to surprising moments, discover 12 secrets behind the RHS Chelsea Flower Show
The RHS Chelsea Flower Show is the most prestigious gardening event in the world — but behind the immaculate borders and medal-winning gardens is a far stranger reality than most visitors ever see.
There has been a garden made entirely from plasticine, a year so wet it was nicknamed the ‘Chelsea Shower Flow’, a mysterious pollen-induced ‘Chelsea flu’, and even a wedding held on the showground itself.
As Chelsea Flower Show 2026 opens to the public on 19th May, discover 12 secrets behind the world-famous gardens.
One of the strangest secrets in RHS Chelsea history is that a full-scale garden was once built entirely from plasticine. It was created in 2009 by television presenter James May using more than two tonnes of modelling clay in 24 colours. The unique display failed to win any real awards – but it didn't stop James from being presented with an ‘RHS Gold Medal’ made of plasticine.
Behind the polished displays, Chelsea has seen its share of chaos. In one year (1932), relentless rain destroyed exhibits – a summerhouse display fell to pieces – and turned the showground into a soggy mess, prompting insiders to nickname it the 'Chelsea Shower Flow'.
While most visitors associate Chelsea with royal appearances, few realise the Princess of Wales has actually worked behind the scenes. In 2019, she co-designed a garden herself — offering a rare glimpse into how even high-profile figures get hands-on at the show.
Her debut Back to Nature Garden, in collaboration with Andrée Davies and Adam White of Davies White, was a forest-inspired plot, with a den, swing seat and treehouse, aimed to highlight the physical and mental health benefits of the natural world.
Read more: Kate Middleton's Back to Nature Garden
One of Chelsea’s more unusual rules is its long-standing ban on garden gnomes. Considered too informal for the show’s aesthetic, they were only allowed once — when the rule was temporarily relaxed for a special centenary display in 2013.
However, the gnome ban has been lifted once more for 2026 – this time thanks to King Charles and the humble Highgrove gnome that takes up residence in his Gloucestershire garden. Celebrities have been enlisted to decorate these miniature figures to raise funds for the RHS Campaign for School Gardening.
Read more: Chelsea Flower Show lifts gnome ban — thanks to King Charles
Visitors only see the finished result, but RHS Chelsea is a very big production. The entire event is built from scratch in 25 days and dismantled in 11 days.
For every Show Garden, like Kazuyuki Ishihara's gold-medal winning Japanese Tea Garden (pictured), teams have just 19 days to build it from scratch — and then only five days to take everything apart again once the show ends. Smaller gardens are built from scratch in 16 days and dismantled in 3 days.
Read more: Monty Don praises Kazuyuki Ishihara's 'flawless' Japanese tea garden
One of Chelsea’s lesser-known secrets is that some materials are strictly off-limits. In recent years, floral foam — widely used in floristry — has been banned due to its environmental impact, forcing designers to rethink how they build their displays.
Often mistaken for a natural product, floral foam is actually a non-biodegradable plastic that releases microplastics, which led to its removal from RHS shows.
Artificial grass has also quietly been added to the banned list, as it doesn’t align with the RHS’s environmental principles — everything you see at Chelsea has to meet strict sustainability standards.
Read more: Chelsea Flower Show: the RHS has banned floral foam at this year's show and The RHS bans artificial grass
While many moments at Chelsea go unnoticed, one marked a major shift. In 2016, Juliet Sargeant became the first Black designer to create a garden at the show. The Modern Slavery Garden was also Chelsea's first social campaign garden – it was awarded a Gold Medal and the People’s Choice Award.
Read more: Chelsea Flower Show designer Juliet Sargeant on why showmanship matters
Chelsea isn’t just about flowers — it has even hosted a wedding. In 2023, garden designer Manoj Malde married his partner Clive on the feature garden he designed: the RHS and Eastern Eye Garden of Unity, marking the first time a marriage had taken place on the iconic showground.
Manoj said: 'How on earth is anyone going to accuse the RHS of being elitist when they are going to have the first RHS Chelsea wedding between a gay Indian man and a gay Irish man?'
For the first time since the Second World War, Chelsea didn’t go ahead as planned. The coronavirus pandemic forced the RHS to cancel Chelsea in 2020. Instead, the entire show moved online — giving audiences a rare look at a completely reimagined, virtual version of the event. The aim was to 'share the joy of gardening' with the nation through collaborations with growers, designers, landscapers and trade stands.
Read more: Chelsea Flower Show 2020 virtual show
Even this carefully curated event isn’t immune to disruption. In 2023, climate protesters targeted a Show Garden — creating a moment few visitors would expect to see at such a refined event. The RBC Brewin Dolphin Garden was left permanently damaged after orange powder paint was thrown across the plants and hard landscaping by Just Stop Oil protesters.
In 2023, Mark Gregory’s The Savills Garden became Chelsea’s first fully working kitchen garden, where produce was grown, harvested and cooked on site — offering a rare behind-the-scenes glimpse of a garden in action.
It was a bold move, but Mark is known for not doing things by halves: his much-loved 2018 Welcome to Yorkshire Garden was also crowned Garden of the Decade in 2020.
Read more: Inside the Savills Garden
Behind the scenes, building a garden can take its toll. Designers often suffer from what’s known as ‘Chelsea flu’ — caused by dust, pollen and long days — long before visitors ever arrive.
Garden designer Nina Baxter once told The Guardian: 'It is difficult to concentrate with lorries continually going past, and when people are stone-cutting, you get covered in dust. But the worst thing is when the plane trees on Main Avenue dump their pollen. It's horrible: you get it in the back of your throat and in your eyes – they call it Chelsea flu. Everyone hopes for a big strong wind overnight so it takes it off the trees all in one go.'
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