Zhang Yanxiang (back) analyzes vegetables for people online with the help of an assistant at a vegetable clinic in Shouguang, Shandong province. Ju Chuanjiang / China Daily

A harried-looking farmer holding a withered tomato leaf appears on the computer screen in front of Zhang Yanxiang.

Speaking through a headset, Zhang asks the farmer to zoom in on the plant.

"It's late blight disease," Zhang says, instantly diagnosing the disease. "Don't worry; you can use a fungicide I developed which will cure it in a few days ..."

So went one of dozens of diagnosis sessions the 39-year-old specialist has each day at the country's first online "vegetable clinic" for growers from as far away as the Xinjiang Uygur autonomous region in Northwest China.

"Farmers are desperate for knowledge about vegetable disease and pest control, as greenhouses are mushrooming in China," said Zhang at the hospital in Shouguang, a city of 1 million residents in East China's Shandong province.

"That presents a niche market for 'vegetable doctors' to thrive in."

With at least one-third of its population and nearly two-thirds of its arable land devoted to growing vegetables, Shouguang has been dubbed China's "vegetable city", supplying more than 100 cities.

The area of China's greenhouse vegetable planting surged 78 percent from 2000 levels to hit 3.35 million hectares in 2008, producing one-fourth of the country's total output, according to Ye Zhenqin, a division chief with the Ministry of Agriculture.

"Zhang is an innovative farmer who learns fast, sometimes from expensive failures," said Wang Peng, a local government staff.

Unwilling to submit to what he deemed the indignity of receiving several sacks of flour a year from relief agencies, Zhang left school to lay bricks in 1986, hoping to take home the 27 yuan ($4.25) in tuition that his widowed mother could not afford to pay.

He never returned to school.