Shekalim 3 - Also on the first of Adar
Another announcement that happened on the first of Adar was about kilaim - growing different species, such as grapes and wheat, together. There is a parallel kilaim prohibition of wearing wool and linen together, representing Abel the shepherd and Cain the earth tiller, and the separation between the two helps rectify Cain’s murder, which somewhat explains the mitzvah.
Around the first of Adar is when the mixture of grains becomes visible above the ground. One can easily transgress this even unintentionally, by having too much of extraneous grains in the mix he sows.
Some people did not listen to the court and kept their kilaim, so on the fifteenth of Adar messengers of the court would go out and uproot the grasses, to shame the transgressors. That did not help though, since the farmers were glad that the messengers would weed the fields for them, and moreover the farmers could use it as fodder. Then the court ordered to throw the grass on the road, but the farmers were still happy because of the weeding. Finally, the court decided that any field with kilaim will become ownerless, and anyone who uproots kilaim will obtain the ownership of this field. This settled the matter.
The Talmud goes into the investigation of why the courts have the authority over people’s possession and can make it ownerless.
Art: Peasants in the Field, Eragny by Camille Pissarro