Hm depends on what kind of plants you got there. Low-tech plants don't really need special substrates like Eco-Complete or Flourite if that's what you mean by just "substrate". What kind of plants do you have?
This just gave me a fantastic idea. Aquatic ladybugs. Aquatic Hamsters. Aquatic Pigeons. I'll make millions.You can take the plants back and get a refund. Don't feel bad, I ran into the same problem. When I was figuring out the same issue you’re having I went as far as talking to Petsmart/Topfin headquarters. They weren't sure what I was talking about since there in the aquarium section (the ignorance of higher up people). All they would have to do is google the plants that they sell and see that they aren't aquatic plants. I was then told that a gentleman from the aquatic research division would be calling me. He did call and his response was that the plants are listed for "aquarium use", however this “doesn't mean that they will last as long as true aquarium plants and they will need replacing when they rot.” The bottom line is that big chain stores can twist words and sayings so the average person thinks they understand, but in all reality we don't and get mislead in their marketing games.
I just did a Google search of the scientific names of the ferns, and neither of them are even aquatic. One actually is commonly found in woodland forests. This is ridiculous. I am merely an ill informed consumer. Damn you for thriving off of my ignorance, TopFin. How is it possible that they can get away with selling these as plants "for aquariums"?