Green Essence Rice, also known as Wu-mi Rice, is a famous snack in Jiangsu Province. It is rice cooked with the sap of the Wu-mi Tree, which is dark green in color, and is one of the most important foods for local residents during the Cold Food Festival. It is mainly for nourishing the body and worshipping ancestors, and is said to have been created by Taoists.

The green essence rice was originally a folk food, which was created as early as the Tang Dynasty.

In the rural areas around Yixing, Liyang, Jintan, Nanjing and southern Anhui in Jiangsu Province, on the eighth day of the fourth month of the lunar calendar, most people would use the leaves of the wu rice tree to cook wu rice for consumption, and the eating of wu rice at the Ching Ming Festival has gradually formed a custom.

The main ingredient used to make the rice is the Southern Candlewood, which is also known as "Black Rice Grass". The specific method of making the rice is to use the branches and leaves of the tree, pound them into juice, soak the rice in the juice, steam the rice, and dry it in the sun. On the "South Candlewood", the Northern Song Dynasty Shen Kuo in the "Dream Stream Brush Tales" also has a record:

South Candlewood, the record of biographies, the "Materia Medica" said that there are many different, fewer people know. For its green essence of rice, color black, is mistakenly used for the Uber, all wrong. This wood type is also, like grass, so it is called the South Candle grass and wood, today's people called the South Heavenly Candle is also.

Southern people are planted between the threshold, stems such as capsules, joints; three or four feet high, LU Qingjing rice production methods ancient and modern. Some first steamed rice, sun-dried, and then dipped in the juice of the leaves of the rice tree, re-steamed and sun-dried nine times, the so-called "nine steam nine exposure", the finished product is hard, can be stored far away from the carries, with boiling water to soak food.

Later, in the Jiangnan area, the green rice is the day of the Qingming day to do the same day to eat, not "nine steam nine exposure". Specific practice is: early summer picking rice tree leaves cleaned, pounded and a little soaked rice, to be a dark green rice fish out to dry slightly; and then the green juice into the pot to boil, cast the rice under the pot to cook rice, cooked rice color green, the smell of fragrance.

The reason why the green rice is called "udon" is that it is made from the juice of the udon tree. Wu rice tree belongs to the azalea family, a kind of evergreen shrub, in the north and south of China are wild, in the Jianghuai area every cold food festival, people will pick the leaves of the tree to cook into Wu rice.

The green rice is not only for the ordinary people's home, more fairy home, that can be served for a long time to benefit the face. "Green essence" two words, give a person the color of the simple and texture of the crystal hard feeling, such as a grain of green gems, so that people have "eat green essence of the rice must be the wind and drink dew, the immortal of the grain food gas" associations. Green rice is also used as an offering at the Qingming Festival in some areas. There are two versions of the origin of this custom:

One version is that it was done in honor of Jie Zhi Tui, a vassal of the Duke of Jin. In order to honor Jie Zhitui, Duke Wen of Jin also ordered that the day Jie Zhitui was burned to death be designated as the Cold Food Festival, and in the following years, fires were forbidden and cold food was eaten on every Cold Food Festival as a sign of remembrance.

Another theory is that the cold food festival originated from the old fire ban in the Zhou Dynasty. At that time, there was a habit of changing the fire in every season. The fire came out at the end of spring, before which people were warned to forbid making fire and to eat cold food. In addition to the custom of eating green essence rice, people also eat a variety of flower porridge on the cold food festival, the most typical is the plum blossom porridge. Song Yang Wanli has "cold food plum porridge" poem as evidence:

Just look at the wax after the spring, sad to see the wind as snow drift. The plum blossom porridge will be boiled and eaten, and the fallen plum blossoms are still good to burn as incense.

See, the Qingming Festival food customs are with the change of the years and more and more diversified.