Walking on grass on Shabbos

[א] (halacha 5)

Question: Is it permitted to walk on grasses or grass on Shabbos?

Answer: It is permitted to walk on grasses or grass on Shabbos, since there is no certainty that one will detach the grass, and he does not intend to detach them (Shulchan Aruch Admur HaZaken OC siman 336 s. 8). The Mishnah Berurah wrote a novel ruling that if the grass or grasses are long, one should be careful not to run on them, because this is a pesik reisha — meaning he will certainly detach [and it is possible that even with fast walking we must be concerned] (Mishnah Berurah 336 s.k. 25). However, many of the Acharonim disagreed with him and wrote that our eyes see that even one who walks briskly (runs), this is not a pesik reisha — and it will not necessarily be detached, and we should not introduce decrees of our own reasoning, and it is permitted to run and walk quickly even on tall grass/grasses (Aruch HaShulchan siman 336 se'if 21). However, in a case where it concerns dry stalks that break easily when one treads on them, in this one must be careful since this is a pesik reisha (Ketzos HaShulchan siman 142 in the Badei HaShulchan os 13).

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