Tang Jing sells yellow "roses", wrapping them in bunches in green paper and colorful ribbons. If you don't look closely, you may not notice that they are actually cabbages.

Such cabbages have been popular gifts in Jiangsu province since they appeared on the market before Spring Festival, which began shortly after Valentine's Day this year. Each cabbage sells for 8 to 10 yuan ($1.30-1.60).

Tang, the manager of Kunshan Yuye Vegetable Planting Base, which is supervised by Nanjing Agricultural University, said the "roses" can be purchased only in winter because they take on their beautiful bright yellow color only during cold days.

Her base is producing more cabbage "roses" for the upcoming Lantern Festival, which falls on March 2 this year.

"It takes four months for the cabbage to grow and show its color," Tang said. "Due to limitations of transportation, most of our customers are from Jiangsu province."

Hou Xilin, a professor of gardening at Nanjing Agricultural University, has spent 13 years researching the cabbage with his team.

"Unlike other yellow cabbages, our cabbage has the exact color and shape of yellow rose petals. The cabbage is not genetically modified, but gained its characteristics through generations of hybridization and self-pollination."

"The 'roses' are very nutritious," Hou said. "They have three times more vitamin C than common cabbages. About 100 grams of the 'roses' contains 156 mg of vitamin C."

He said the cabbage can resist low temperatures and its vitamin C content rises and yellow color becomes brighter as the temperature drops.

"We are now researching equipment that will allow people to grow the 'roses' on their balconies. An experiment on my own balcony has proved fruitful. About 100 such sets of equipment will be tried out for feedback."

He said that the fibrous organic material used to grow the cabbage contains no pesticides or worm eggs. After harvesting the cabbage, that material is recycled by his team.

Kang Hai, 23, a resident of Kunshan, Jiangsu, bought a bunch of the cabbages for his girlfriend. He said: "If she doesn't like them, I can eat them up."