There is no great harm in doing so. As long as you respect the area it comes from and not make a mess doing so, then it is fine.
Its also fine to introduce them to your tank, though you might find a few critters hitch hiking into your tank. They are not dangerous, but some may say they look unsightly. Things like planarian or common hitch hikers, and no one likes them. Other than that, its a case of seeing how the plant does. Despite it being warm during the summer, its still colder than what the tropicals like, so you may find it does not take to the higher temperatures, but you wont know unless you try.
Hope that help.
Cheers.