Clive Aslet enjoys Hampton Court flower show with his young sons.
Squelch, squish. ''I like that noise,'' said my six-year-old son Charlie as we slithered and sloshed our way through the entrance gate. Of course children like this year's Hampton Court Flower Show: they can get up to their ankles in mud, without grown-ups being able to say a thing.
But there is another reason. Inside the crèche tent is Mr Rotavator, wearing a straw hat and dungarees - a different figure from the Mr Motivator with whom he could be confused. Out of a net basket he lifts a newly hatched butterfly, its wings still damp.
"It's a Painted Lady," cries one bright spark. Butterflies are placed on to children's outstretched fingers and then put back into the basket, except for the one that flutters through a crack in the tent into what looks deceptively like sunshine, but will soon be monsoon conditions.
We are now being shown seeds and fruit, starting with coconuts (the largest seed in the world) and ending with the "most dangerous fruit in the world", the huge, sharp-spiked cone of the aptly named Big-Coned Pine. Then it is time to pot up some plants. After half an hour, Charlie has a rucksack full of seeds.
Mr Rotavator's determination to get children gardening is shared by pop singer-turned-gardener Kim Wilde. "I'd like children to get excited about looking at the state of their environment," says Wilde, whose book, Gardening With Children, was inspired by her son, Harry, nine, and daughter, Rose, seven. "We make miniature gardens together out of snail shells, seed heads, twigs, lavender and string."
Given that a third of young children surveyed by Country Life some years ago did not know that oaks grew out of acorns, this is heartening to hear.
Gardening also helps an increasingly obese nation understand more about healthy food and take some exercise. Children are therefore a theme of this year's Hampton Court Flower Show. They have directly contributed to the design of three gardens and are enticed to enjoy others - for example, the Playscape Community Play Garden, sponsored by Play England.
This coincides with the Government's new Learning Outside the Classroom Manifesto, which states that "every young person should experience the world beyond the classroom as an essential part of learning and personal development". The Department for Education and Skills sponsored the Growing Schools Garden, designed by TV gardener Chris Bearshaw with the help of 30 schools; it won Best Show Garden.
Alton Infant School in Hampshire boasts a garden, with vegetable plots for each class. A microcosm, from designs by the children, has been recreated at Hampton Court.
"It's brilliant - we've been learning outdoors for years," says teacher Anne Foulkes. "We garden organically - that's why there's a slug experiment. We learn about saving water, composting and recycling. Five years ago, the school found £30 from its budget to start a vegetable garden, but there's been no official budget since."
The charity Playground Partnerships, backed by Woolworths, has been established to help schools develop their playgrounds. "The children designed the Hampton Court garden using bits of paper, which we then drew out on the playground to size. The children were not allowed to plant out the garden because of health and safety." There is always a snake in paradise.
Foulkes shows Charlie the chicks. "I don't want chicks at our school," he announces. "I want lions." He wanted the acer plant he had potted with Mr Rotavator, too, but it had gone missing. An emergency ice-cream saved the day. And eventually the plant was recovered. Phew. Because, you know, a plant is for life, not just a Flower Show. As Kim Wilde says: "He could still be caring for it when he's 25."
• Hampton Court Palace Flower Show ticket hotline: 0870 906 3791 (public line) or 0870 906 3790 (RHS members). Tickets from £13; children aged 5-15 years £5; under-5s free. The Magic of Gardening with Mr Rotavator workshops, tomorrow and Sunday from 11am to 3.30pm at half-hourly intervals. For further information, visit www.rhs.org.uk/flowershows