It was a life-changing moment for Sue Biggs when her mother presented her with a fork, a trowel, and a packet of seeds, on her seventh birthday.

For it engendered a passion for gardening that led, 48 years later, to her appointment as director general of the Royal Horticultural Society (RHS), the most important body of its kind in the world.

That was three years ago, and Sue still describes her job as “a dream come true”.

But it would have been more like a nightmare to anyone less ardent about horticulture than she is.

For her first task on taking control in August 2010 was a necessary but painful re-structuring of the society, including axing three of its directors, merging several key roles, reducing running costs that had soared unsustainably high, and increasing a membership that had stayed static for years by becoming less bureaucratic and more outgoing.

A tough call indeed, and the fact she answered it so successfully is, one feels, due as much to her captivatingly unpretentious and humorous personality as to the formidable skills that took her to the top during her 30 years in the international leisure industry, where she won many awards, including the Golden Globe for outstanding business achievement.

Since she has headed the RHS, membership has grown to more than 400,000 – the highest in the society’s 209-year history – and more than 2m people enjoy the RHS annual world class shows.

And her determination to raise the profile of lesser-known aspects of the society’s charitable work, particularly its Community, Arts and Science initiative, has so far inspired more than 50 per cent of schools in the UK to sign up to the RHS campaign for school gardening, while record numbers of people have joined RHS community schemes to transform their environments.

Her plan for the next five years is for the RHS to invest £27m in the future of horticulture, funded by £18m from the sale of its Lawrence Hall in London, and the £9m her team aims to raise from donors and sponsors.

A native of Yorkshire, Sue came to London in 1981, and after a brief spell in West Hampstead, moved to Richmond.

In 1986 she and her husband bought a house near the river in Twickenham.

Twelve years later, her marriage over, she took a riverside house in Sunbury, where she spent 17 years before moving to her present home in the Tilt area of Cobham last year.

It is, she says, a little Victorian cottage, that will be her off-duty pride and pleasure for years to come.

Meanwhile she has been joyfully overseeing the Hampton Court Palace Flower Show, to which she was devoted, and attended every year as an ordinary visitor, long before arriving at the RHS.

“I have always thought it the best gardening show in the world, not only for its huge range of exhibits, but its incomparable setting,” she said.

Under Sue’s direction this year’s show will, for the first time, be divided into three zones – Grow, Escape to the Country, and Inspire – where gardens, plants, food and shopping reflect their individual themes.

Grow will feature nurseries, plant stalls, potting demonstrations and stands selling the best in gardening equipment. Escape to the Country will have the Country Living Pavilion, a Great Tastes marquee, where visitors can sample “artisan” foods, and a section devoted to grow-your-own fruit and veg.

Inspire, sponsored by Ecover, will focus on innovation and making the most of outside space.

Many people who never engage in gardening themselves, go to the Hampton Court show for the exquisite beauty of the show gardens.

There will be 34 of them this year, with themes as diverse as the three witches in Shakespeare’s Macbeth to the threat posed by waste on the world’s oceans.

For obvious reasons, Sue was reluctant to name her personal favourite in this year’s show.

Finally she admitted that, if she had to choose one thing, it would the butterfly dome where visitors will enter the steamy green heart of tropical jungle, populated by 3,000 butterflies.

“It will not only be spectacularly beautiful, but remind us of the importance to the environment of pollination,” she said.

One thing’s for sure. Sue’s years of experience as an ordinary visitor, plus her powerful role as head of the RHS, should guarantee that this year’s Hampton Court Palace Flower Show – already noted as the largest and most beautiful show of its kind in the world – will be the best yet.

l Hampton Court Palace Flower Show will run from Tuesday, July 9 to Sunday, July 14. The first two days will be for RHS members only. (Why not join now, and save 25 per cent off a year’s membership?)

On the remaining days, all-day tickets for the public will be £29.50 or £19 for entry after 3pm (2.30pm on the Sunday) and £23 and £15 respectively for RHS members. But each paying adults can bring two children aged under 16 free of charge.

Show opening hours are 10am to 7.30pm Tuesday to Saturday and 10am to 5.30pm on the Sunday, For further information, or to book tickets in advance, ring 0844 338 7536 or visit rhs.org.uk.

To win tickets to the flower show read this week's Surrey Comet, Kingston Guardian or Elmbridge Guardian.