Yan Ying, also known as Yan Zi, was a famous politician in the Spring and Autumn Period. He once assisted Duke Ling, Duke Zhuang and Duke Jing of Qi. It is said that Yan Ying is not tall and not attractive, but he is resourceful.
Once, when Yan Ying was sent to the state of Chu, the King of Chu and his ministers wanted to ridicule and embarrass him. The King of Chu held a banquet for Yan Ying. In the middle of the banquet, several soldiers escorted a man to the hall. The King of Chu said to Yan Ying, "This is a man from the State of Qi who was caught stealing in the State of Chu. Do you people from the State of Qi like stealing?" Everyone laughed and waited to watch Yan Ying's making fool of himself.
Yan Ying had already noticed that the King of Chu and his ministers were acting, so he stood up calmly and said to the King of Chu, “I heard that when the orange tree grows south of the Huai River, it produces sweet oranges. If it is transplanted north of the Huai River, the fruit will turn into sour and bitter tangerines. The taste of the fruit produced by the same plant is very different. Why is this? It's because of the difference in soil and water! The person in the Great King's Palace did not steal in Qi, but learned how to steal when he arrived in Chu. Could it be that Chu's soil and water make people become thieves?” These words choked the King of Chu, unable to respond.
The idiom “Oranges change with their environment” refers to the variation of the same species due to different environmental conditions.
晏婴，也称晏子，齐国人，是春秋时期著名的政治家，曾经辅助齐灵公、庄公、景公。据说晏婴身材不高，其貌不扬，但足智多谋。
有一次，晏婴出使楚国，楚王和大臣们便想奚落一下晏婴，让他出丑。楚王设宴招待晏婴，宴会中间，几个士兵押着一个人来到殿上，其中楚王对着晏婴说：“这是个齐国人，因为在楚国偷盗而被抓，难道你们齐国人都喜欢偷盗吗？”众人哄笑起来，等着看晏婴的笑话。
晏婴早就看出是楚王和大臣们在演戏，于是站起来，不慌不忙地对楚王说：“我听说橘树生长在淮河以南时就结出甘甜的橘子，如果将其移栽到淮河以北，结的果实就变成又酸又苦的枳了。同种植物所结果实的味道却大不相同，这是为什么呢？这就是因为水土不同的缘故啊！大王殿上的这个人在齐国时不偷盗，到了楚国后却学会了偷盗，莫非是楚国的水土会使人变成盗贼么？”一席话噎得楚王张口结舌，无以应对。
南橘北枳，比喻同一物种因环境条件不同而发生变异。
