The Torah prohibition of "Tolesh" forbids detaching a fruit from its tree, or a plant from the ground, on Shabbat. One violates this prohibition by pulling a fruit off a tree even if he uses his weaker hand. Whereas normally performing an action with one’s weaker hand relegates the violation to the level of "De’Rabbanan" (Rabbinic enactment), in the case of Tolesh, one violates the Biblical prohibition regardless of which hand he uses to remove the plant, since the use of the weaker hand has no significant effect on the nature of the act performed. In fact, one violates this prohibition even by biting the fruit off the tree. The Mishna Berura (Rav Yisrael Meir Kagan of Radin, 1839-1933) laments the fact that many people in his time were unaware of this Halacha, and would bite fruit directly off trees on Shabbat. He goes so far as to recommend appointing guards in orchards on Shabbat to warn people not to commit this transgression.
As a safeguard against violations of Tolesh, the Sages enacted that one should not smell a fruit that it still attached to a tree on Shabbat, as one who smells the fruit might then detach it in order to eat it. However, Hacham Ovadia Yosef clarifies that this prohibition forbids only going up to a tree in order to smell a fruit; if one walks into an orchard, he is allowed to smell and enjoy the fragrance of the fruit, and one may even specifically recite the Beracha over fragrances and enjoy the smell of the orchard. Furthermore, this prohibition applies only to edible plants. It is entirely permissible to smell inedible fragrant plants – such as flowers or Hadasim – and one may even hold them with his hands (obviously, without detaching them) and recite the Beracha over the fragrance.
It is forbidden to place flowers in water if this will cause the flowers to open. Thus, for example, one may not place roses in water on Shabbat unless they have already fully opened. Even though the flowers are, of course, already detached from the ground, it is nevertheless forbidden to put them in water in such a case, since this will have a significant impact upon their development.
The Rama (Rav Moshe Isserles of Cracow, 1530-1572) rules that even if the flowers have opened, or even if the plants do not have flowers, one may place the flowers or plants in water only if they had been in that same water before Shabbat. Under no circumstances, according to the Rama, may one place plants in fresh water on Shabbat. Hacham Ovadia Yosef, however, based on the ruling of the Rashba (Rav Shlomo Ben Aderet of Barcelona, 1235-1310), rules that one may place plants in fresh water on Shabbat, unless this would cause the flowers to open. For example, it would be permissible to place hadasim in fresh water.
A vase of flowers is not Mukseh on Shabbat, and there is no reason to be concerned that moving them with their water will promote their growth in any way. Therefore, it is entirely permissible to move a vase with flowers on Shabbat.
Summary: It is forbidden to detach a fruit from a tree on Shabbat with either hand, or by biting it directly from the tree. It is forbidden to smell a fruit that is attached to a tree on Shabbat, but one may smell inedible fragrant plants even though they are still attached to the ground. It is permissible to enjoy the fragrance of an orchard on Shabbat, as long as one does not go up to trees to smell their fruit. One may place flowers or other plants in water on Shabbat, except in the case of flowers which have not yet opened, and will likely open as a result of being placed in water. It is permissible to move a vase of flowers or other plants on Shabbat.