If you believe there is unlawful activities going on at the neighbor's property (such as drug dealing), you can call the police to report your suspicions.
Many cities and counties have ordinances (such as grass cannot be taller than some specified height, trash cannot be stored in the yard, car cannot be parked on grass, etc.). You can report to the city or county if things like that are evident at your neighbor's property.
You likely cannot successfully sue the neighbor because "landscape depreciates value of [your] property".
If both properties are in the same homeowners' association, you can get the HOA to enforce its landscaping requirements.
You can review the specific facts with your attorney to find out your legal options.
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