The RHS Chelsea Flower Show, formally known as the Great Spring Show,  is a garden show held for five days in May by the Royal Horticultural Society (RHS) in the grounds of the Royal Hospital Chelsea in Chelsea, London. Held at Chelsea since 1912,  the show is attended by members of the British royal family. 
Highlights to the Chelsea Flower Show include the avant-garde show gardens designed by leading names with Floral Marquee at the centrepiece. The Show also features smaller gardens such as the Artisan and Urban Gardens.
The first Royal Horticultural Society Great Spring Show was held in 1862, at the RHS garden in Kensington. Before this date the RHS had held flower shows from 1833 in their garden in Chiswick, which themselves had been preceded by fetes.  The Kensington Garden was chosen as a site because the flower shows in Chiswick were experiencing falling visitor numbers due to problems such as poor transport links.  The Great Spring Show was held at Kensington for twenty-six years but in 1888 the RHS decided to move the show to the heart of London. The site chosen was the Temple Gardens, situated between the Embankment and Fleet Street, which had a recorded history dating back to 1307 and which were said to date from the time of the Knights Templar. The roses for which these Temple Gardens were famous were alluded to in Shakespeare's Henry VI Part 1.  Using three marquees requisitioned from the old Kensington shows, the 1888 show was a success with exhibits from both amateurs and commercial firms. By 1897 five marquees were being used with many of the best known plant and seed merchants being attracted to the event including Suttons and Sons. 
In 1912, the Temple Show was cancelled to make way for the Royal International Horticultural Exhibition. Sir Harry Veitch, the great nurseryman, secured the grounds of the Royal Hospital, Chelsea for this one-off event. It proved such a good site for an exhibition that the Great Spring Show was moved there in 1913, where it has taken place almost every year since.  There have been two breaks for world wars. 
The RHS first became involved with the Chelsea Hospital in 1905. Three years before, it had leased the grounds of Holland House in Kensington to hold what was first advertised as a Coronation Rose Show, but which turned into a more general show (with not many roses) by the time it actually opened in June. Two further two-day summer shows took place at Holland House in 1903 and 1904, but then, to the general satisfaction of exhibitors and press, a three-day Summer Show was staged in the hospital grounds, a more spacious site than Holland House had allowed, with room for five tents. The Summer Shows reverted to Holland House for the years thereafter, except in 1911, when both it and Chelsea proved unavailable, and the Show was held at the Olympia exhibition hall.
The Royal International Horticultural Exhibition of 1912 used the grounds of Chelsea Hospital as the site for the show, and for 1913, the Great Spring Show was moved there. The first Chelsea Flower Show opened on May 20. [ failed verification] The Summer Show reverted to Holland House. Despite the First World War, the show was held 1914–1916, but was cancelled in 1917 and 1918.
By the 1920s, the Chelsea Flower Show had returned to its previous form; the famous Chelsea tea parties were established and Royal visits resumed. In 1926 the show was held a week late due to the General Strike.[ citation needed]
In 1937, King George VI and Queen Elizabeth celebrated their Coronation Year, and an Empire Exhibition was staged to mark the occasion. It featured wattles from Australia, pines from Canada, gladioli from East Africa and even a prickly pear from Palestine.[ citation needed]
The show was cancelled during the Second World War, as the land was required by the War Office for an anti-aircraft site. Some doubt arose as to whether the show would resume in 1947. The majority of exhibitors wanted a postponement, as stocks of plants were low, staff much depleted and fuel for greenhouses was obtainable only with special permits, but Lord Aberconway (then RHS President) and the RHS Council felt strongly that the show should resume as soon as possible. The show eventually successfully went ahead in 1947.[ citation needed]
The show went on to increase in popularity throughout the second half of the 20th century and crowding became a major problem. Crowding within the tents had been a recurring issue during the interwar years, but was always handled by increasing the number of tents; photographs show heavy crowds in the open, especially in the vicinity of the rock gardens. As the 1970s progressed, attendance at the show climbed by 6,000 visitors in a single year (1978). In 1979, crowding became so severe in the mornings that the turnstiles were temporarily closed. It was decided to open the show at 8 a.m. the next year, and close it at 8.30 p.m. in the evenings, with a reduced price for entry after 4 p.m., to try to draw people away from the morning timeslot; a one-way system was also laid out in the marquee (a solution that had been rejected as impractical 20 years earlier).
The new arrangements for the show were successful in 1980, and a majority of the Council voted for the imposition of a ceiling on the number of tickets sold. However, visitor numbers continued to increase, and in 1987 the turnstiles were closed again. In 1988 a cap had to be placed on the number of visitors attending the show due to problems that were occurring with overcrowding.  A limit of 40,000 visitors per day was imposed – a reduction of 90,000 in total from the previous year – and members were charged for tickets for the first time. An immediate response was a fall in attendance; by April, ticket booking was so slow that national advertisements were taken out to encourage people to come to Chelsea, and the original announcement that tickets would not be available at the gates was rescinded.
In response to issues with attendance numbers, the council began to look seriously at the idea of moving the show to a larger venue. Battersea Park, Osterley Park, and Wisley were suggested; one proposal was that Chelsea should be limited to plant sales, and the sundries rerouted elsewhere; the firm Land Use Consultants was also hired to prepare a feasibility study. However, after considering these options, it was concluded that the show should stay at Chelsea. Despite this, the show's programme was expanded into other venues, with the Hampton Court Palace Flower Show taken over in 1993; the increased options for both members and for exhibitors meant that the intense criticisms and conflict of the 1980s over the future of the show did not return.
The Chelsea Flower Show is attended by 157,000 visitors each year (a number limited by the capacity of the 11-acre (4.5 ha) ground), and all tickets must be purchased in advance. From 2005 the show was increased from four days to five, with the first two days only open to RHS members. The show is extensively covered on television by the BBC. An official DVD of the show is produced on behalf of the RHS by ONE TWO FOUR. Several members of the British royal family attend a preview of the show, as part of the royal patronage of the RHS. The area of land devoted to show gardens increased steadily between 1970 and 2000 and the show has become an important venue for watching trends. New plants are often launched at the show and the popularity of older varieties revived under the focus of the horticultural world.
Highlights from the 2011 RHS Chelsea Flower Show included The Irish Sky Garden by Diarmuid Gavin, based on the idea of a restaurant in the sky. Other notable gardens included the HESCO Garden by Leeds City Council, who reconstructed an impressive and idyllic working water wheel in the grounds of the Royal Hospital.
The 2011 show also saw the introduction of the new Artisan garden category, which was created for designers who use natural materials. 
In 2023, for the second year, the show was sponsored by The Newt in Somerset.   At the show, Catherine, Princess of Wales, hosted the first children's picnic at a newly created garden at the show with pupils from ten schools from the RHS's school gardening campaign invited. 
There are four grades of award presented – gold, silver-gilt, silver and bronze – in each of the awards categories. Bronze grade exhibits do not actually receive a medal.
This section needs additional citations for verification. (May 2023)