Before we get to your question regarding muktzeh, we must first discuss the potential problem of uprooting a plant from the place where it is growing. The Shulchan Aruch[1] states: “Regarding a plant pot (atzitz), even if it has no hole (she’eino nakuv), one should be careful not to take it from the ground and hang it from pegs or vice versa, whether the pot is made of wood or pottery.” In general, planting and uprooting apply only to things that are growing in the ground. Nevertheless, we consider a potted plant sitting on the ground to be nourished from it.[2] Therefore, distancing the atzitz from the ground or bringing it closer to the ground is forbidden on Shabbat under the categories of uprooting or planting, respectively.
One would assume that within a house, considering the space and materials in between the plant and the ground, the plant’s nourishment is only from the soil in the pot and there is no connection to the ground. On the other hand, poskim rule that one may not pull things off even potted plants that are inside the house.[3] However, there could be distinctions based on the material from which the house is made, as there are various opinions as to what type of buffer under the atzitz serves as a sufficient separation. Metal and glass certainly break the connection between the plants and the ground.[4] There is much discussion regarding a case in which part of the plant (not its roots) extends beyond the separation.[5] There is further discussion regarding whether the floors in most homes constitute a separation.[6]
The Tehilla L’David[7] infers from the Shulchan Aruch’s ruling[8] that the problem of moving an atzitz arises only when one moves it from the ground to a place detached from the ground, e.g., hanging, or vice versa. In contrast, it is permitted to move the atzitz between two similar places, even if it passes through a different type of area in the process. This is a strong but certainly not simple or unanimous contention.[9]
Even if we can resolve the aforementioned issue, we still must deal with the matter of muktzeh. Soil is a classic muktzeh item, as it is not a utensil, a food, or a similar item that is slated for a Shabbat appropriate activity. Yet, if one sets soil aside for a specific appropriate purpose, it can be moved.[10] How do we consider the soil in an atzitz? The Tehilla L’David[11] surmises from the discussion above that muktzeh is not a problem, since the sole basis for the questions about moving an atzitz is the possible violation of planting and uprooting. The rationale is that the soil does serve a purpose; it serves the plant (and is part of the plant pot[12]), which adorns the house. Some claim that even if the soil is considered to have a function, it is like a kli shemelachto l’issur (a utensil usually used for a forbidden purpose), as it helps plants live and grow, which is something one may not be involved with on Shabbat.[13] Such an object is permitted to be moved only when it is to be used for a permitted purpose or because the location it occupies is needed. Still others maintain that it cannot be moved for any purpose.[14]
In general, there is a machloket regarding whether vegetation that is growing is muktzeh when there is no fear that one will uproot it improperly. The Taz[15] and Magen Avraham[16] say it is muktzeh; the Machatzit HaShekel[17] cites those who are lenient. The Mishna Berura leaves the matter undecided.[18] If one regularly moves a plant pot from place to place, then muktzeh, at least, is likely not a problem.[19]
Two of our time’s foremost authorities rule that one should not move an atzitz on Shabbat.[20] It is unclear what the exact basis of their rulings is. The simplest advice is to arrange matters before Shabbat so that there is no need to move the plant pot, thereby avoiding the significant problems we have discussed. Nevertheless, we cannot fault one who relies on the opinions that one can move an atzitz, especially she’eino nakuv, from place to place, at least in a case of need. (Moving a vase with flowers in it is certainly not a problem.[21])