Grow your own: go to school and get gardening

"What's that?" asked one child, pointing at the actual bean, which now looked like an empty pouch. I explained that the bean provided the vital food to enable the plant to start growing. Once the roots were big enough, its use was over. "Wow," he said, "that's amazing. And we can eat them, too?"

His lack of knowledge isn't surprising. On the same day that we launched the competition, a poll of 3,000 people on behalf of the Home Grown Cereals Authority demonstrated a huge lack of knowledge about where our food comes from.

Almost a third think oats grow on trees, just under a fifth believe eggs are a vital ingredient in making bread, and one in four teens think bacon comes from sheep.

If you don't know the source of your food, what hope do you have of ever eating the right stuff? At the beginning of this week I was speaking at a conference at City Hall on obesity.

We were picking up on research which had been carried out in London and New York and the figures make grim reading. In NYC nearly 40 per cent of four- to eight-year-olds are overweight or obese.

In the UK, 10.9 per cent of kids entering school are obese and 12 per cent overweight, but by Year Six these figures have risen to 21.6 per cent and 14.7 per cent respectively.

The problem is hugely exacerbated in poor neighbourhoods where low-cost supermarkets don't sell fresh produce, and fast-food restaurants (chicken and chips is just 50p) circle the schools like vultures.

What's all this got to do with school gardens? A lot, I believe. According to a survey conducted by the National Farmers' Union, if you get children growing and cooking food, 93 per cent of them go home and say they want to eat fresh food.

In New York, Mayor Bloomberg has issued 1,000 licences for street vendors to sell fresh produce from Green Carts in deprived areas, an idea I want to see happening in our London boroughs, along with an extension of street markets.

The Mayor is already calling for limits on how many junk-food outlets should be allowed near school gates and questioning the presence of chip vans often parked right outside the schools.

Growing your own in your school yard doesn't just get kids in touch with where food comes from, it gets them out of doors and exercising.

More to the point, it's fun, and if you can turn exercise into play, chances are the children will keep on doing it.

We've had many enquiries and letters since launching last week and I've heard some great ideas. One school already grows its own lavender which the kids pick to turn into lavender bags to sell at the school fête.

Another has been combining gardening with carpentry lessons: the kids build the raised beds out of planks, so they're involved in gardening, literally, from the ground up.

Another said it was logged into its local Freecycle and getting all its tools for free. A great idea for quirky containers to grow produce in, too.

Plants can be grown in virtually anything, provided you add some drainage holes, and the weirder the containers, the more the kids get a kick out of the process.

I've seen herbs growing in shoes and rows of beans sprouting from upturned hats. Old suitcases, trunks and chests are perfect.

The first 50 schools to register will get free seeds from Duchy Originals, which further brings down the costs. And you don't need much space: nooks and crannies around school yards can make perfect places to start a growing revolution. You might even end up selling the veg at your school summer fair.

FREE ADMISSION TO KEW GARDENS

Kew is currently training a new batch of volunteer guides. Throughout February, 17 trainees will be giving "assessment tours" in which they will be judged on all aspects of guiding.

There will be two assessors on each tour but Kew also needs 10 members of the general public to act as "guinea pigs" on each tour.

Tours last for one hour and start from the Guides' Desk, just inside Victoria Plaza, at 11.30am or 2.30pm.

In return for your help, Kew is offering free admission to the Gardens for the day.

Please phone 020 8332 5604/5633 or email tours@kew.org to book a place.