The calendar, which costs £9.99, has been available on the Perennial website as Perennial launches an extended evening advice line (0800 093 8543) until 8.30pm on the first Wednesday of the month from 3 November. More than 85 per cent of those the charity helps – 1,200 last year – are of working age.
Director of services Sheila Thomson said pride and fear of refusal were among the barriers stopping people taking the first step in getting help from the charity. "We hope that by offering an extended hours service each month will enable more people to get in touch."
Fellow Perennial director Anita Bates said she could not thank the courageous models enough.
"We're thrilled to be able to offer this fun, tongue in cheek, calendar that will no doubt make a cracking Christmas stocking filler, but the message behind it is a serious one. We'd like to be there for more people."
This is the latest in several fundraising stunts by the group, who call themselves the Grubby Gardeners and have raised thousands for the charity.
Founder Michael Perry, of Thompson and Morgan, said: "I’m sure you remember the Calendar Girls, then we saw firemen, marines, even rowers, but somehow gardeners had never de-clothed for charity. So I’d been hatching a plan for a few years, looking for a range of horticulturists who might be up for it."
Pictures for the calendar were shot by professional photographer Debbie Monique Jolliff, the granddaughter of the acclaimed bulb company founder Jacques Amand.
She said: "We had great fun on the shoot - everyone was very relaxed and took it all in their stride. The venue was incredible and we hope you enjoy the results."
The charity is also reviving an annual fundraiser in 2015 - a century after the original event was put on hold because of the First World War.
The calendar boys are: Michael Perry, new product development manager, Thompson and Morgan, David Lewis, head gardener, The Roof Gardens, Kensington, Trevor Burke, gardener, The Roof Gardens, Kensington, Neil Miller, head gardener, Hever Castle, Kent, Ryan Beauchamp, trainee gardener, Hever Castle, Kent, Matthew Western, trainee gardener, Hever Castle, Kent, Andrew Wain, head gardener, Wiltshire, Ben Pope, head gardener, Sussex, Darran Jaques, owner, Urban Creations, SW London and Surrey, Andrew Lane, formal gardener, RHS Wisley, Rocky Coles, gardener, Wellingborough, Northamptonshire, Alec Jones, masters student (Landscape Management) at the University of Sheffield, Daniel Stanton, BSc student (Horticulture) at Writtle College, Essex, Marcelo Serafim, amateur gardener, Leicestershire, Tom Frost, amateur gardener, London, Ben Jones, freelance horticulturist and designer, Cambridge