The Chelsea flower show is to break with tradition by showing an overtly political art installation attacking the shortage of equipment for troops in Iraq and Afghanistan.

The work depicts the outline of a body drawn in white roses on a black plinth, with blood spatters shown by red petals. According to the artist, Tony Smith, it symbolises Britain sending its soldiers into combat without adequate protection.

Chelsea, which opens on May 20, is not only the main event in the gardening year but also marks the beginning of the Establishment’s summer season. The gala preview is attended by members of the royal family, cabinet ministers and FTSE 100 chief executives.

“I was surprised they even accepted something as political as this,” said Smith, He added: “While we’re spending lots of money on health and safety to try and make our country risk-free, we’re sending soldiers to Iraq and Afghanistan without proper body armour.”

Bob Sweet, organiser of the show, which is expecting more than 150,000 visitors, said it welcomed works that were a “rallying cry”.

“We’re really interested in the value of Tony Smith’s exhibit as an arresting statement and an arresting sculpture,” said Sweet.

It is the first time the artist, who started gardening only in 2000, has exhibited at Chelsea. The installation by Smith, 42, from Haywards Heath, West Sussex, is entitled More Questions than Answers? The plinth holding it will sit in a dark pool filled with green duckweed, surrounded by a black wall.

Other attractions at Chelsea will include a pair of rare orchids being flown in from Grand Cayman in the Caribbean. Both the ghost orchid and the wild banana orchid are native to the Cayman Islands and are usually subject to an export bar. The wild banana orchid, the national flower of the Cayman Islands, will be presented to the Queen when she visits the show.

Times recommends

• Here comes the glass sun – garden honours Beatle
• Gardening tips: 10 things to know about Horny Goat Weed or Epimedium
• Diarmuid Gavin shares tips on how make your garden fun and funky