One of the prohibitions on Shabbat is that of Zorei'a, planting or watering seeds for them to grow. The question arises whether one is allowed to take herbs or plants, such as Hadasim, and put them in water on Shabbat to prevent wilting. We deal with a case of plants that are specifically intended for fragrance, and are thus not considered Muktzeh. Would it be permitted on Shabbat to fill a vase with water and place Hadasim in the vase?
The Shulchan Aruch explicitly writes (321:11) that one may water a plant that is no longer attached to the ground. Thus, one may add water to a Hadas branch, for example, or place it in a new vase with water, on Shabbat.
However, certain flowers, such as gardenias, are often placed into water in order for the plant to open. Chacham Ovadia Yosef, in Yechaveh Da'at, as well as Rabbi Moshe Halevi, in Menuchat Ahava, rule that it is forbidden to place such a flower in water on Shabbat. Although placing a plant in water to prevent wilting is permissible, one may not put a flower in water on Shabbat for it to open. Thus, if one removes such a flower from the vase to smell it, he may not return it to the vase if it had yet to open.
Summary: One may place a plant in a vase with water on Shabbat to prevent wilting, provided that it is intended specifically for fragrance, and so it is not Muktzeh. One may not, however, place a flower such as a gardenia in water on Shabbat for it to open.
