Shulchan Aruch mentions the custom of decorating the Shul with trees (since Shavuot is the day of judgement for fruits), and flowers (to commemorate the foliage that appeared on barren Har Sinai). For various reasons, it is not the Chabad custom to decorate the Shul with trees and flowers, but this may be done at home.
Flowers and decorative leaves or branches which were cut and arranged prior to Shavuot are regarded as a decoration and are not Muktzah. Therefore, when necessary, they may be moved on Shavuot. However, if some of the flowers are not yet in full bloom and exposure to additional moisture will induce them to blossom further, the vase must be moved very gently so that the water level remains constant.
When all flowers are already in full bloom and exposure to additional moisture will not induce them to blossom further, the following further leniencies apply:
- On Shavuot, one may take flowers out of the vase of water. One may also return the flowers to the same vase, as long as the original water was not changed.
- On Shavuot, one may place the flowers in a new vase that was prepared and filled with water before Chag. One may also add flowers to a vase which already has flowers from before Chag.
- On Shavuot, one may top up the water in the vase if necessary, but the ratio of the new water must be less than half of the total. One may certainly not replace the existing water.
A potted plant should not be moved due to two concerns – Muktzah and aiding plant growth. [In principle, these issues are subject to differing Halachic opinions and other variables.] If the potted plant accidentally overturns, or some soil spills out, it should be left alone. [If doing so will create a hindrance or inconvenience, a Rav should be consulted.]
For practical purposes, a potted plant should generally be treated as attached to the ground. Therefore, one may not water it at all or detach any of its leaves or branches. One may not lean on a potted tree or shrub, move it with his hands even ever so slightly, place anything in its branches, or remove anything caught in its branches.
Flowers, branches or leaves that were detached (regardless of the cause) on Shavuot are Muktzah. The same is true even if there is just a doubt whether it became detached on Shavuot. It goes without saying that they are Muktzah when still attached to the ground.
One may smell flowers and plants on Shavuot – even if still attached to the ground (and hence Muktzah). One should remember to make the appropriate Brachah. However, one may not smell attached fruits.
