The 221st prohibition is that we are forbidden from cultivating trees during the seventh year [shemittah].
The source of this prohibition is G‑d's statement,1 "[It is G‑d's Sabbath during which you may not plant your fields] nor prune your vineyards."
The punishment for transgressing this prohibition is also lashes.
The Sifra says: "The prohibitions of planting and pruning were already included.2 Why were they singled out? To make a comparison — just as planting and pruning have the special quality of applying both to the land and to trees, so too, the prohibition includes any type of work which applies both to the earth and to trees."3
The details of this mitzvah are also explained in tractate Sh'vi'is.
