Keeping vegetables fresh for the 2,000 kilometers it takes to get them from Ningxia to Hong Kong has not been easy.

"It requires high-standard refrigeration through the process," Yeung said. "We put choi sum into a cold warehouse with a temperature of 4 C after picking, and it stays there for eight hours."

The choi sum is then packed into boxes with bottles of ice and loaded into refrigerated trucks.

Vegetables from Yeung's farm come with quick codes, which allow buyers to look up information about them, such as where and when they were grown.

The codes also enable the farm to record information about who has picked the vegetables and how much they have picked.

"The codes not only ensure quality but also make it easier for us to calculate wages," said Yeung, who added that in the future, he hopes to harvest by machine, which will mechanize the entire process.

In addition, Yeung is trying environmentally friendly ways to grow vegetables in a bid to protect nature.

"We try to use less pesticide and fertilizer," he said.