Githu not only established contacts with the vendors, but also secured orders from two restaurant owners who each week buy more than 20 kilograms each of his vegetables. He delivers twice a week.

Peter Mukami is one of the vendors he supplies. Mukami has been in the business for five years, and says that over that time the market for Chinese vegetables has grown steadily.

"In fact, demand has drastically outstripped supply," he said.

Another trader, Paul Ng'ang'a, said he has traded in Chinese vegetables for 10 years. Prices are depressed at the moment because of a surfeit of supply, he says.

"We're selling a kilogram of Chinese cabbage for about 50 cents. When supplies are low, they can sell for double that."

He personally goes to the farm where he buys vegetables, he said.

"The rise in demand has been in line with the growing Chinese population in Nairobi, but Indians and a growing number of locals eat these vegetables, too."

Increased demand among locals for organic and nutritional food is also driving supplies, he says, adding that he has picked up tips from the Chinese on how to prepare the food, and he passes these on to locals.

"Trading in this market is more than just buying and selling; it is becoming personal."

The Chinese population grew markedly in 2008 and 2009, when work began on building the 50-km Thika highway, which links Nairobi with the town of Thika.

The work, done by two Chinese firms, cost $360 million and was completed in 2012.

It was the biggest infrastructure project in the region before work began on the standard-gauge railway, the 609-km line that will link Nairobi and the port city of Mombasa, which is being built by the China Roads and Bridges Company.