Anything but firm action by the Owners Corporation (O/C) could easily result in the practice of residents annexing areas of the Common Property garden-space becoming endemic.
Whilst I don’t disagree with the community garden solution, it’s hardly firm action, and shouldn’t that solution be something initiated by the Executive Committee on behalf of all Proprietors and not an expedient solution to appease one Proprietor who has Breached the (standard) By-Law 4 to their personal benefit?
So my answer to the question would be to agree with those of my fellow contributors who recommend the issue of a Notice to Comply to the gardener, together with a requirement that they either reinstate the Common Property or pay the O/C’s costs to do so.