Fertile minds: How a garden in Hampton Court could help alleviate crop shortages in Africa

Sometimes you wander around a flower show looking at the names of the gardens' sponsors and wonder why they're spending all that money. But that's not the case with the garden being backed by Kirstine Dunhill's charity, Send a Cow, at Hampton Court Palace Flower Show. As she says: "We're just farmers helping farmers."

Unlike most expensive show gardens, this is a charmingly home-made affair – designed by a supporter and built by the charity's staff. As well as promoting Send a Cow, the garden is practical, showcasing two intriguing ways of growing vegetables, more of which later.

Send a Cow was set up in 1988 by a group of farmers from the West Country who wanted to help people in Uganda. "At that time, these were farmers who were very much into using the latest chemicals and pesticides," says Dunhill. "They wanted to bring that to Africa, but when they got there they realised this approach just wasn't feasible for the local people. So they began to think instead about giving animals as a sustainable source of manure – and so Send a Cow was born."

Growers in Africa have been affected by climate change, war and the loss of almost a whole generation to Aids, reducing the levels of soil fertility and horticultural know-how alike. Yet ingenious minds have been thinking up solutions to these seemingly intractable problems, which are being showcased by Save a Cow at Hampton Court, and which will appeal to gardeners in both Africa and Britain.

The first of these is the bag garden – a tall hessian sack of soil sent to families trying to survive incipient famine. Deep enough to grow potatoes in, you can also cut holes in the sack and plant things up the sides too. It can be watered easily when irrigating fields isn't possible. The bag garden would do equally well on a tiny British patio or balcony.

My favourite solution, however, is the "keyhole" garden. Instead of a separate compost heap, this is built into a circular raised bed. Liquid from the rotting matter then goes straight to your veggies, instead of seeping down to those Leylandii living by your compost bin (see right for "how to").

"The thing that African people are often most keen to show you is their keyhole garden. You see all this dry red earth, then you see lush green leaves in rich, dark soil – the benefits of the relationship [Save a Cow is fostering] between manure and growing," says Dunhill. "We don't do toilets, we don't do schools. Every penny goes to growers, to farming."

The Hampton Court Palace Flower Show starts on Tuesday (members) or Thursday (general public), ticket hotline: 0870 842 2234. Send a Cow, www.sendacow.org.uk

Nature's way: Garden sustainably

1. Make your own natural pesticide

Soak seven cups of marigold leaves, one cup crushed chilli and seven bulbs of garlic in five litres of water. Add a piece of soap, three spoons of baking powder and some wood ash. Use after four days.

2. Make your own plant 'tea'

Fill a bucket with chopped docks, comfrey and clover. Cover with water, adding a pinch of ash. Cover and stir daily. After a week, remove the leaves and use as you would a diluted liquid feed.

3. Make a keyhole garden

Draw a 3m circle and edge with rocks. Mark a tiny central circle with posts and make a compost "basket" inside with sticks and string. Fill bed with soil sloping down from centre, leaving a tiny path for access. Fill the basket with vegetable waste and enjoy your fertile plot.