The Queen will be one of the first people to visit the Chelsea Flower Show today, as the finest horticulturalists from all over the world exhibit their immaculately designed gardens.
Home-grown talent will vie with designers from as far afield as Australia and Dubai to win the coveted title of best show garden at the world-renowned exhibition.
And for the first time in its century-long history, an amateur will compete with professionals for the award.
Organisers of this year's Chelsea Flower Show are hoping this year's theme will come up roses with contestants, who are being asked to cast their eye over history for inspiration.
The Chelsea Flower Show will mark the centenary of the First World War by asking entrants to arrange flowers around the theme of old and new conflicts.
Designers have drawn on family experiences of war from the Somme to Afghanistan to create displays for this week's show at the Royal Hospital Chelsea.
No Man's Land: ABF The Soldiers' Charity Garden to mark the centenary of the First World War represents a landscape marked by the fighting in northern France, including trenches, a mine crater pond and the yew trees found in war cemeteries.
Broadcaster Alan Titchmarsh has admitted he was "hurt" by the BBC's decision to sideline him in this year's Chelsea Flower Show programming - saying he was made "an offer I had to refuse", he told the Radio Times.
Titchmarsh, 65, who has been replaced by Monty Don admitted:
"Yes, I suppose I was hurt, because I know people enjoy you doing it as much as I loved doing it.
"But they probably felt it was time for a change and may well be right. Was I dumped for Monty Don? You might say that. I couldn't possibly comment. I don't feel dumped."
It was announced last year that Titchmarsh was leaving the show, with the BBC saying in a statement: "The way the Chelsea coverage will be presented across the BBC has changed for 2014, and Alan decided to step away from next year's show."
Titchmarsh told Radio Times: "I'm not bitter. I was disappointed but I'm not a grudge-bearer. You have to move on."
This year, Titchmarsh has created a Royal Horticultural Society (RHS) garden for Chelsea and the BBC has booked him for an interview to talk about his creation for the Britain In Bloom scheme.
After almost 30 years, top gardener and TV presenter has said that the Chelsea Flower Show "doesn't get more demanding," after marking 50 years in horticulture.
Titchmarsh will this year be designing a feature garden at the world famous flower show for the Royal Horticultural Society (RHS) Britain in Bloom scheme, which is also celebrating its half century.
"I've got a great team. When you build a garden at Chelsea you're working with the big boys, it doesn't get more demanding, more testing than this. I want to give it the best shot," he said.
The garden follows a journey in horticulture from his birthplace in Yorkshire to the coast of the Isle of Wight where he has a home and garden.
Presenter Alan Titchmarsh is stepping down from the BBC's Chelsea Flower Show coverage after 30 years as its host.
The gardening guru decided to leave the show after a revamp of broadcasts from the event.
"I really enjoyed my 30 years of presenting Chelsea Flower Show coverage for the BBC and wish the new team every success," Mr Titchmarsh, 64, said.
He has increasingly turned his attentions away from the BBC, with an afternoon ITV chat show and a series on Classic FM following his departure from BBC Radio 2.
Two men have dressed as gnomes at the Chelsea Flower Show. A historic ban on gnomes at the show is being overturned this year to mark its centenary.
Celebrities have been given a sneak preview of this year's Chelsea Flower Show, ahead of its public opening. The Queen will also make a special visit later today.
Celebrities have flocked to the world's most famous flower show for a sneak preview ahead of the Queen's official visit. The Chelsea Flower Show marks its centenary this year.
Gnomes, appearing at the Chelsea Flower Show for the first, will be sold on auction site eBay to raise money for the RHS Campaign for School Gardening.
The decorated figures will all be auctioned off on eBay from today to raise money for the £1 million RHS Centenary Appeal, marking 100 years since the first Chelsea Flower Show.