[Bonanza]

I've said it before and will say it again. Notherners move here and want palm trees because it represents a tropical look and a look they've never had before. They are attracted to Queen palms because they are less expensive than other palms. They are the cheapest palm a landscaper can buy. Other than the fact that are not suitable for our plant zone, they are trash trees. They need more care than other palms and cockroaches and vermin are attracted to them.

I seriously doubt that a 12" deep plant barrier will do the job the OP thinks it will do, but I wish him luck. He probably should forget about a "plant barrier" and get rid of the palm..