A bleach solution
should work. Just make sure to soak the plants in clean water after with extra dechlorinator. IIRC, it's 1cup of bleach per 5gallon bucket. I could be mis-remembering, however. There are plants that won't take well to being bleached, such as moss. And many plants will die if their roots are bleached. Still.. better than introducing golden velvet, ich or, even worse, leaches! to your tank. Not to mention hundreds of bacterial or viral strains that your fish from who knows where may or may not have any immunities to.
>.> another option would be to try trading some of your current plants with other people in the area for different plants, and growing your own to seed your tank with. You can always grow plants out in a bucket, too. Just feed 'em dirty tank water and throw a halogen light over them. (well, that works with a lot of plants, but not the difficult ones...)
Another thing to be aware of is that a lot of plants out in the swamps today are actually invasive species from people like you and me who import exotic plants from other countries for our aquariums. Tossing out the "cuttings" sometimes results in those plants growing wild and choking out the native wildlife. If you see plants that you would normally have to import, feel free to take them.
The forest rangers probably want you to.
Transplanting plants found in the 'wild'?
