Can I Eat on Grass on Shabbos and Yom Tov?
Shailah of the Week by Rabbi Zvi Nussbaum
Rabbinic Coordinator, Kosher Hotline Administrator for the Orthodox Union
The Mechaber of the Shulchan Aruch writes that on Shabbat one may not wash their hands on top of grass or vegetation because if water spills, it could cause growth (which is a melacha of zorea, planting).
Rema extends this to any use of water and says that it’s a good thing to refrain from using water in a “gan” (translated as grassy area), after eating something messy and then using water to wash your hands or spilling the remaining droplets of one’s drink on the grass.
Even though we usually say that a davar she’ein miskavein – an act that is unintentional – is not assur, since water always flows to the lowest point, when water spills it is a psik reisha – an unintended act with an inevitable result – it will drip on the grass and cause the grass to grow.
The Mishna Berura note 30 points out that if this area, like a vegetable patch or dense forest, is larger than 70 by 70 amos it's a carmelit (karpif) and one cannot carry there at all. However, grassy areas that are used to service a bungalow colony are like a backyard and are not included in this prohibition, provided that they are enclosed in an eruv.