# One should be careful not to spill any liquid or even to spit on plants on Shabbos. <ref> 39 Melachos (Rabbi Ribiat, vol 2, pg 267-8) </ref>
# Urinating on a plant isn't a violation of Zoreah (because the caustic fluid doesn't help the plant). <ref>S"A 336:3, Mishna Brurah 336:28, 39 Melachos (Rabbi Ribiat, vol 2, pg 267-8) </ref>See the halacha about urinating into dirt (Melachet Lash).
===Removing a Sukkah covering===
# If it rained and water collected on a Sukkah covering (shlock) and by removing the covering the water will spill onto grass it is only permitted to remove the cover if the grass is fully saturated (such as after it rained steadily for a long time and the ground hasn’t begun to dry). However, if the grass isn’t fully saturated one may not remove the covering if by doing so one will spill rainwater on the grass. <ref>39 Melachos (Rabbi Ribiat, vol 2, pg 268-70) </ref>
==Putting flowers in a vase==
# One may not put tree branches in a vase with water on Shabbat; however, one may return them to water unless there are flowers on the branches. On Shabbat one may not add water to a vase with flowers or branches; however, on Yom Tov one may add water. <Ref>S”A 654:1, Mishna Brurah 336:54, Shemirat Shabbat KeHilchata 26:26 </ref>