Guy Barter was born on a farm in a hamlet miles from anywhere in southwest Wiltshire. “We were known as the Baa-rters, because we had so many sheep,” he says. It was his grandfather who ran the farm, while his father worked as a probation officer and social worker, but he was surrounded by keen gardeners and got his own allotment at an early age.

“Although there weren’t many there like me. I used to experiment with making my own fertiliser formulas using ingredients from the allotment shop and keeping records to see what worked best for each different group of crops.”

Chemistry was his favourite subject at school but he had no clear vocation at that stage. “Out of indecision I drifted into the health service, where I worked as a microbiology technician for 11 years, first in Dorchester and then in London.” Then, one day, it dawned on him that he wasn’t actually suited to the job he was doing. “I was 29 with a house in west London but I decided the time had come to be a bit brave so I signed up for a horticulture degree at the University of Bath.”

It was a life-changing move. Guy thrived on the course and relished the summer work placements that were an integral part of it. “I specialised in hardy nursery stock and plant propagation in the vegetable industry. I love the science of it. An intellectual conundrum has always appealed to me.”

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After graduation he worked there full time for a year before spotting a job vacancy at the RHS gardens at Wisley. That was in 1990 and, apart from a three-year sojourn working for Gardening Which?, he has been with the RHS ever since.

“I was running the Wisley trials field, with responsibility for 35 different crops every year. It was a tremendous opportunity to learn, because I always had the support of a selection of relevant experts. With their guidance I would set up growing processes and, from time to time in those early days, subsequently have to work out what exactly had happened when things went wrong,” he says. “You soon learn that some short cuts are more successful than others. And it all gets easier with time. Nothing beats experience.”

You'd be surprised at the number of people who every autumn would ask why the leaves on their trees were turning brown

After four years he was lured away to Gardening Which? “I wasn’t particularly wedded to the outdoor life, so when the job of senior researcher came up it seemed like another interesting challenge.” Within a couple of years he was running the advice service so, when Wisley decided to develop its own advice service, Guy was an obvious recruit.

“I started off with two others in a Portakabin in the Wisley car park although, even in those early days, we used to get 10,000 phone calls and about 7,000 letters a year – many of which contained plant samples that were squashed or smelly by the time they arrived.”

As a man who loves a conundrum, Guy relished the challenge of fielding a never-ending series of largely random questions. “Obviously the same things tend to come up year after year. You might be surprised at the number of people who contacted us every autumn to ask why the leaves on their trees were turning brown and falling off. I’ve also had more than a few people asking why their tomatoes were covered in flowers, even though they kept pulling them off to allow the fruit to form. I managed to keep a straight face most of the time.”

In the 18 years he spent with the advisory service, Guy’s team grew to ten, he oversaw the development of a smart new advisory centre and witnessed the dawning of the computer age. He also pioneered the production of more than 1,000 leaflets covering the most commonly asked questions. “I am proud of those,” he says. “Effectively, they add up to a free-to-use encyclopaedia of practical horticulture.”

I also like to experiment with trends, such as No Dig or cover crops

Then, in 2016, his job title changed from chief horticultural advisor to chief horticulturist. “It meant I didn’t have to manage a large team of advisors any more, freeing up all the time that used to go on pay reviews and recruitment to concentrate on horticultural matters.”

He now provides information and advice (highly regarded and much appreciated) to members of the press and has a general remit to keep looking outside the organisation. His wife, a botanist whom he met at Gardening Which?, also works for the RHS and in their spare time the pair are keen allotmenteers. “Georgina was inspired by a visit to a cut flower farm to take over part of my allotment, but we soon agreed she needed a plot of her own.”

On his allotment Guy, who once oversaw the RHS’s Model Vegetable Garden, grows almost everything. “I always look at the RHS trials to choose varieties and take a train-spotterish delight in trying something new. I have designed my allotment to need minimal water, but also I also like to experiment with trends, such as No Dig or cover crops.”

It is hard not to feel a twinge of sympathy for the allotment holders on either side of Mr and Mrs Barter, although if they ever have a problem with autumn leaf fall or troublesome tomato flowers, they won’t have far to go for advice.