What do the remaining residents say? The SC represents all owners not just one. Depending on cost it may require a vote by the OC unless the SC are allowed a certain amount of expenditure without having to put it to the OC for a vote.
A practical matter are the type of planter boxes and what they are being attached to. It may look good but where will the water go? Constant moisture between the planter and the whatever it will be attached to will cause problems down the track. It just needs proper consideration that’s all.