Having evolved from its origins as a society for head gardeners and garden managers, the Professional Gardeners' Guild represents pretty much anyone who makes their living through professional gardening. And through its trust, the guild helps fund those in full-time horticultural employment to gain qualifications "for the benefit of gardening's profile as a profession".
But with its image problems - evidenced by prime minister David Cameron's misguided comments last year comparing gardening to litter collecting - and generally low pay, what does a career in professional gardening have going for it? "It is a fantastic career," says Arnold. "You get to work outside, be creative, have a degree of freedom in what you do and you are providing a source of pleasure, excitement and stimulation for others."
And according to Arnold, far from being the day-dreaming idealists commonly portrayed, professional gardeners can be ambitious and career-minded, with many working towards a head gardener's position at prestigious gardens in the UK or abroad. "To do what we do takes dedication," he says.
Indeed, opting for a career in heritage or conservation horticulture and taking responsibility for some of the country's garden and landscape crown jewels is not for the faint-hearted. Many historic gardens are used as stage sets for films and TV dramas, and they also contain some of the most valuable plant collections in the world. Anyone choosing to work in these gardens may well be responsible for conserving rare plants and crafts skills to hand on to the next generation, as well unlocking historical mysteries and symbols to tell the stories of how these gardens were created and what they mean.
Working in a botanic garden, meanwhile, involves the maintenance of an enormous range of plants from around the world, and includes scientific study into the way they are named. This can involve travelling to many parts of the world to look at plants growing in the wild. The head gardener or garden manager is responsible for the upkeep and development of the botanic garden.
When it comes to working in the specialist areas of heritage and botanic gardening, gardeners need more than the prerequisite green fingers and a love of plants. As with any professional gardener, they will work day-to-day planting, pruning, weeding, mowing and mulching, the difference being, however, that they will be working on gardens that are, in some cases at least, hundreds of years old.
"We look after gardens dating back to Elizabethan times when plants were grown in different ways and using different techniques," explains National Trust head of gardens Mile Calnan. "Our remit is to demonstrate those techniques or recreate historic styles and create a living history."
The trust relies on 450 gardeners and a 1,500-strong army of volunteers to take care of the one of the world's greatest collections of historic gardens and plants. To maintain a steady supply of skills and know-how, the trust is launching two new qualifications, developed with in partnership with Reaseheath College, Cheshire and supported by the National Garden Society - a foundation certificate and a diploma in heritage gardening.
For more information, see www.growcareers.info/heritage
National Trust certificate
A bespoke National Trust heritage gardening course, the certificate has been designed to develop the essential practical skills needed to operate in a significant heritage garden open to the public. It combines the RHS level 2 certificate in horticulture (theory), the trust's certificate in horticulture, the college certificate in garden history and National Proficiency Test Council certificates in manual handling, brushcutters and mowers.
Graduates can undertake further training provided they have secured a post with the trust and can also apply to do the two-year diploma to develop deeper skills, knowledge and experience in heritage gardening, taking them up to craftsman level.
"I believe the trust's diploma offers a new and exciting opportunity for people wishing to develop a career in the sustainable management of heritage gardening," explains Calnan. "Trainees will be able to work in some of the most famous heritage gardens in the country and learn about garden conservation from the experts."
While relevant qualifications range from NVQs to full horticulture degrees, a gardening professional's greatest asset will nearly always be practical experience. Having worked their way up from gardener, a head gardener at a historic garden is responsible for looking after and developing the garden as well as managing the staff. Even historic gardens need to develop and change, so the head gardener will also design and plant new areas in keeping with the tradition of the garden.
At Arundel Castle, head gardener Martin Duncan's CV features head gardener positions for private residences in London and Bermuda, as well as for the late King Hussein and Queen Noor in Jordan. Now ensconced in West Sussex, he leads a team of two horticulturists, two groundsmen and two gardeners, one a volunteer turned apprentice. Between them they care for the quirky Collector Earl's garden, a grass labyrinth, stumpery, willow arch, wild flower garden, tropical house, organic kitchen garden, rose garden, herb garden and the 1852 vine house.
"Her Grace (the Duchess of Norfolk) loves the gardens and has her input and as head gardener I have mine and we work together to achieve highstandard results throughout the gardens," says Duncan, who favours gardeners with experience gained from working with the National Trust, English Heritage and the Royal Parks.
"Those who come straight from college do not have adequate practical experience. If you open to the public you have to be meticulous and show a high degree of professionalism. It has to look good, make people feel good and have general appeal. Presentation is foremost."
Former head gardener now consultant and fellow of the Institute of Horticulture, Alan Sargent says the key to a successful career in this field is teamwork. Head gardeners need to have the vision and management skills to guide their team, while all members need to pull together to create the high standard gardens both owners, operators and paying visitors expect. "A head gardener can have all the horticultural skills in the world but if they can't manage they might as well give up. They must gain the respect of their team," he advises.
Fiona Dennis, coordinator of the Historic & Botanic Gardens Bursary Scheme, which enables enthusiastic and committed horticulturists to increase their skills through training placements in a range of historic and botanic gardens, agrees with Sargent on the role that teamworking plays. She counts it as an essential skill, alongside a passion for plants and a commitment to high standards.
She also cautions that working in a botanic or heritage garden today is no place for shrinking violets. With so many gardens heavily reliant on tourists and visitors to fund their survival and ongoing development, gardeners have a more public face today than ever before. "They must be able to interact with a public that increasingly recognises the important role that gardens play in our lives," says Dennis. "It's a fundamental part of working for any heritage or botanic garden today."
Gardener career path: You will need natural green fingers and a love of plants. Relevant qualifications range from National Vocational Qualifications to horticulture degrees, but your biggest asset will be practical experience.
Head gardener career path: Head gardeners are usually practical gardeners with many years of experience working in gardens, from privately-owned estates to National Trust properties, having gained a formal qualification from a horticultural college.
Botanic garden curator: A strong plant knowledge is key to running botanic gardens, so professional horticultural qualifications are recommended, along with a period of work at a suitable garden - for example RHS Wisley and Royal Botanic Gardens, Kew.
For more information, see www.growcareers.info/heritage