If your cat suddenly starts ignoring the litter box and relieves itself in a fragrant flower bed, you should take steps to wean the animal off this unwanted behavior.
Check the condition of the tray
Make sure your cat's litter box is in good condition and cleaned regularly. Cats often don't want to use a dirty litter box, so the first thing to look at is regular cleaning and replacement of the litter.
Change the location of the tray
Move the litter box to another location that is convenient for the cat. It should be easily accessible and located in a quiet and calm corner.
Buy additional trays
If you have multiple cats or a large home, it may make sense to add one or more extra litter boxes. Each pet needs their own litter box, otherwise they may start using other places (your flower bed) as a toilet.
Close off access to the flower bed
If your cat continues to use the flower bed as a toilet, block access to the area. Netting or other barriers will do the trick.
If the problem continues despite these steps, it is best to contact your veterinarian or behaviorist for further advice and guidance.