I believe the jungle vals propagate by sending runners with new shoots. Not sure about the banana plant, and I would use a liquid fertilizer as well. Especially with a banana plant. But it depends on the plants you have.
Bananas propagate a few different ways. Letting them just go can make new babies as the runners that shoot towards the surface can start to grow new tubers under them. You can snip off a big leaf that's growing from the tubers and let it float around. It can grow roots from there. Also, the plants will shoot runners under the gravel and new plants can pop up wherever. Really cool plants. They grow in the wild all the way from Florida to Maryland so they are pretty hardy and easy to grow.