The RHS has been criticised for promoting young and inexperienced designers "at the expense" of more established gardeners at Chelsea Flower Show.
Judges gave six golds in 2014 compared to 10 in 2013. Both year's shows featured 15 show gardens.
Established designers Luciano Guibbelei, Cleve West and Adam Frost were among gold winners, while of the crop of the up and coming designers the RHS is promoting around its 2013 Horticulture Matters report, only 26-year-old Hugo Bugg won gold.
RHS director Sue Biggs defended the RHS choice of designers as good for the sector, adding that it had not led to a lower quality set of gardens overall at the show.
Just four of the Chelsea designers had built show gardens at the event before - three won gold this year. Two designers had not built any RHS show gardens, while the rest had not built main avenue show gardens in one of the most inexperienced line-ups in recent years.
Garden writer Anne Wareham said: "It is promoting youth, though, isn't it? And not just there - all the emphasis in trying to get children gardening too. I think it's a poor use of their resources.
And a new group called ‘Old Hort’ has called for a "more balanced" view of horticulture.
The 140-member group, founded via Twitter this year by former Houghton Lodge head gardener Andrew Bentley, follows a similar organisation forming this year titled ‘YoungHort’ which is open to under-25 year-old gardeners and has been championed by celebrity gardeners such as James Wong – as well as the RHS.
Bentley said: "There has been a lot of focus recently on getting young people into careers in horticulture with the younghort initiative but some of the press has been at the expense of older, more experienced gardeners. While we support their cause and the initiative they have taken it is important to remember that people over 25 years old also need to feel that horticulture is worthwhile both as a career and a hobby. Older people coming to horticulture usually have as much enthusiasm as young people with the added bonus of life skills, experience and maturity. People already striving to forge a career in horticulture form the majority of subscription paying members of organisations set up to support the industry."
He added: "I would like to think that the designs for Chelsea show gardens are chosen on merit primarily and there is no ageism involved. I think that there is a current trend towards particularly promoting young people in horticulture by all the major organisations and the oldhorts group was formed in response to this, to provide some balance. I don't think good design is age-related."
RHS Chelsea Flower Show manager Saul Walker said: "There’s a range of ages at Chelsea – a good mix. There’s a few new guys doing their first Chelsea and a lot of publicity around young ones this year. But then there’s Cleve West, Charlotte Rowe, Jo Thompson and even Matthew Childs has done Hampton Court successfully and moved up to Chelsea so there’s probably only one or two who are brand new."
James Wong said: "I've heard plenty if people say what about ‘old hort’ but that's just hort to me. If you’re 30 there’s no problem working in hort. Horticulture is the most equal opportunity industry I know for age, sex, ethnicity but for younger people it’s genuinely hard to get in and they need guidance."
Meanwhile, Bentley has tweeted the Institute of Horticulture, which runs the Young Horticulturalist of the Year competition: "Maybe a balanced view of horticulture as a career for those of us too old for #younghorts would be good? See @OldHorts too!"