I checked several references and none lists ferns as being tolerant of salt. So, I would say that ferns are injured like other herbaceous plants, by salt, showing stunted growth, leaf burn and some dieback. A large amount in the soil may kill roots or may not.
Are you thinking of using salt as a herbicide? That wouldn’t be recommended because salt:
• Accumulates in soil
• Damages soil structure
• Injurious to many plants, trees, shrubs nearby
• Readily leaches and contaminates groundwater
• Increases runoff of heavy metals
• Increases soil erosion
If you would like to tell me more about what you are trying to do with your ferns, I may be able to help more. Thank you for using our service.