If I were a landlord, the no. 1 thing I'd be concerned about is what renters are storing in my basements/storage areas. For ex., you mentioned the room is "for brushes," suggesting paints, solvents, etc. [What could be worse?] I'd be most concerned about the non-living areas, the utility and storage rooms. And a locked door and bogus story just raises more red flags.
I suggest hide the plants (that's why they give advance notice of inspections; landlords don't want to see some things); and use your risky lock the room (do nothing?), stand your ground and hope to avoid problems approach as a backup plan.