Anyone for tea?: The nation's beverage of choice shares a genetic bond with one of our favourite shrubs, as Anna Pavord discovers on a visit to India

When we left home to spend January wandering in India, the first buds were just opening on the white camellia in front of the house. On our return the bush was covered with flowers, but they were all a soggy brown. That was a sure sign that we'd missed a horribly wet month. We inherited the camellia when we bought the house and it still surprises me that it does so well, facing as it does to the south, exposed to the east and mulched by a fair amount of builder's rubble, thinly disguised under a layer of leafmould.

Behind the camellia is a long window and the first flowers always appear on the back of the bush, looking in through the glass. That's a treat, given that January weather is not made for lingering outside. But because we don't want too much of the window's light blocked out, I generally trim the camellia after it has finished flowering. The aim is to create a rounded, compact shape, a loose piece of topiary, which involves nothing more drastic than snipping off the overambitious new shoots that leap out from the top of the bush. Camellias don't need regular pruning, but ours submits to its annual trim without complaint.

Many of our garden camellias come from Camellia japonica, which grows wild in China and Japan. In India, we saw its cousin, C. sinensis, the tea plant, growing in the huge estates around Munnar in the Western Ghats, the mountains that separate Kerala from neighbouring Tamil Nadu. I'd never before seen a tea plantation and hadn't realised how extraordinary they look in the landscape. The Munnar estates were well established, the tea bushes perhaps 50 or 70 years old. Set out originally in parallel rows on the hills, like the contour lines on a map, the bushes had gradually broken out from this geometric grid and spread into comfortable amoeba shapes. But completely flat on top. That's what made them look so extraordinary en masse.

Acre after acre of shiny green rolls over the slopes around Munnar, swirling round huge smooth rocks, dividing briefly either side of a beaten earth track, all the greenery growing at exactly the same height. Although ecologists will perhaps disapprove of these monocultures, I found the sight mesmerising. The whole landscape became a vast topiary garden, a clipped construct like the 17th-century maze at the Monasterio de San Lorenzo at Santiago de Compostela. To me, the grooves in the swirling green that marked the individual bushes had the same soothing quality as the lines raked in a Japanese sand garden.

The Munnar estates, at more than 1,500 metres, are among the highest in the world. Tea plants need very wet summers and dryish winters but a temperature that does not fluctuate too much between the seasons. They evidently grow rapidly as, talking to the pickers, we learnt the bushes could be picked over at least once every three weeks. Sometimes, given the right conditions, they produced new growth within a week. Uncut, a tea bush can grow into a tree, at least 15 metres high.

Camellia leaves are stiff and leathery. Foliage on the tea bushes, although evergreen, is softer and thinner. Some pickers still plucked by hand, at incredible speed, filling sacks they carried on their backs. Most of the pickers we saw round Munnar used shears, specially customised for the job. Fixed on one blade was a vertical sweep. Fixed on the other was a net bag, held rigid by a wire frame that matched the shape of the sweep. Clipping over the tops of the bushes, the sweep pushed the soft young shoots into the bag. When that was crammed full, the picker emptied it into one of the big sacks dumped strategically through the plantation.

Apparently, a good picker can pluck 35 kilos of leaves in a day. In a sack, that looks a lot, but it barely registers as a contribution to the three million tons of tea harvested every year. Here in Britain we drink more of the stuff than anywhere else in the world: 165 million cups a day, 60 billion cups a year.

We stayed outside Munnar on an old tea plantation, in just the kind of bungalow you'd hope to find in such a place: wooden walls, tin roof, a garden planted with stokesia and asters, roses and marigolds. In the evening, you could climb up on to one of the vast, dough-smooth boulders that litter the landscape here and watch the sun set behind the hills; as its blood streamed through the sky, an evening wind would start up and owls hooted from their holes in the banyan trees.

From this place, the Windermere Estate, you could walk down through tea plantations into Munnar on a track that keeps you on the opposite side of the river from the chaotic main road. A swaying footbridge delivers you to a place where you can buy more sorts of tea than you ever knew existed. On the way you pass the High Range Club, where early planters held flower shows and gymkhanas, and prettied up the club grounds with hibiscus and frangipani.

Of course it was economics, not romance, that brought the planters here in the first place. In the 1830s, the East India Company lost its monopoly of the tea trade between Britain and China.

That's when attention turned to India, where a type of tea, Camellia sinensis var. assamica grew wild in Assam. The Cornishman, Albert Congdon of Duloe, was typical of the adventurers who arrived in India in the 19th century to develop new plantations. Aged 18, Congdon sailed to Calcutta in 1861 with Captain Rogers RN, who already owned estates in Assam. Congdon was taken on as manager of the Assam Tea Company at Burdwar in the Ganhati district and eventually acquired 800 acres of tea-growing country in Assam, employing some 2,000 pickers.

In Cornwall today, the trade is happening in reverse. An expert from Assam is shortly arriving at the Tregothnan Estate, near Truro, to work with the head gardener, Jonathon Jones, who seven years ago planted Britain's first commercial tea plantation. As you'd expect, the rate of growth is slower than in India. They started picking at Tregothnan in 2005, plucking the first flush in late May and picking over the bushes at six-weekly intervals after that. I've never been a tea drinker, but the enchanting thought of Cornish-grown tea may yet convert me.

Tregothnan single estate tea is available from Fortnum and Mason, London W1 (020-7734 8040), The Orangery at Kensington Palace, London W8 (020-7376 0239) and Partridges, London SW1 (020-7730 0651). Expect to pay around 30 for 15 grams. Their blended tea is available at 6.99 for 25 tea bags. If you want to try growing your own, tea plants are available from the Tregothnan nursery, near Truro, Cornwall TR2 4AN, open by appointment for collection only. They can also send plants by mail order. For more information call 01872 520325, fax 01872 520291, email bigplants@tregothnan.com or check out the website at www.tregothnan.com.

Tea plants are only likely to succeed outside in areas as mild as Cornwall. Otherwise grow them in pots and bring them into a frost-free but cool shelter for winter. They like acid soil (pH 4.5-6.5) and light shade. Mulching with pine needles or leaf mould helps retain moisture and maintain the pH level of the soil