How do you interest a young child in something as intrinsically conservative as gardening? The answer must always be to start at the fast end, the end which offers results next week, not next year or next decade. The long-term pleasures and disciplines can follow later.
Keen adult gardeners are always ready to point out that one of gardening's great pleasures is that you go on learning. But for a child, everything is new, and that first-time fascination with novelty is the best of allies for a teacher.
The most productive way to proceed with children is make them see there are two sides to gardening, and that each can be fun. There is the business of making things grow - the plant side of it, and the playing with spaces - the ideas side.
Productive gardening - growing food - has unfailing appeal to children. The best place to begin is not at the start of the cycle - the chores of digging and manuring - but with picking the crop. Let them smell the warm fruit, handle it as it is passed down from the ladder, or shucked into a bowl on the back doorstep. If they show signs of wanting to plant as well as consume, choose easy crops, such as salads, beans or new potatoes.
Bean pods and salads come in a wide range of colours, which can make for extra fun. Forget plants that need spraying or careful protection from birds - failure is no encouragement. Go for volume. Let them sell their beans to their grandparents.
Crops that produce their own seed for future generations show how life in the plant kingdom works. So beans or potatoes that can be saved to start next year's crop have more appeal than other vegetables which, to a child, may seem dead-end plants. Saving seed is a kind of production in itself.
Nasturtiums and sunflowers and marrows and gourds produce easily identifiable seed that will always grow again the following year. Collecting the seed can be part of the fun, especially with plants such as impatiens, with its powerful seed ejection mechanism.
Why not grow the squirting cucumber Ecballium elaterium, with its bitter little gherkin pods that shoot juice and seeds yards away at the touch of a finger.
When it comes to gardening as space-making, adults always praise the value of surprise - the hitherto hidden vista, the sudden blaze of colour, the opening out of a small space into a larger one. But children, who are so much smaller, have a different relationship to space. The clipped evergreen allee and the enclosed arbour are manipulations of nature contrived to please adults. To give children the same degree of pleasure they can be smaller still.
Children love small spaces where adults cannot go. It might be a tunnel of honeysuckle or sweet peas, or a forest of bamboo stems. For a faster effect, you might plant miscanthus, a tall, clump-forming grass that rises to 3m every year. You could make a maze of it, or a tight spiral - a labyrinth.
You might make the same thing from long willow rods pushed into the ground. The new top growth might then be woven to make a roof.
Live or dead, willow is a pliable material full of sculptural possibilities, and capable of doing in a year or two what takes decades with yew topiary. It may be short-lived but the ideas and inspiration involved are the same.
Some gardens represent a journey through life, and the idea of giving a garden an objective is worth offering to children. It might be simply the progress from childhood to old age, or from water-dwelling animals through land animals to birds and bats. The value comes in encouraging children to think of gardens as places where provocative ideas can be made tangible.
Children can also be encouraged to make gardens containing some symbolic significance - personal initials perhaps, or a name, in a pattern of flowers. It is less simple than it sounds. The great and good of gardens have always done it. It indicates ownership of the garden, and a willing responsibility for its upkeep.
How about making a fountain? Or a really complicated guinea pig run - a miniature landscaped assault course? The important lesson is that garden spaces need an idea, a reason to be there, and that the planting is only a dressing of that space - albeit an important one.
Adults and children alike can be liberated by discovering that gardening is not just about making plants grow and dealing with pests and diseases.