You could probably just trim off most of the leaves, remove the plant from your terrarium, trim off any broken roots and transplant it to a new place, but that wouldn't "propagate" it.
There is a nice plant section on the forum link I'm suggesting. Just go to the main site, then the forums, and then the section on plants. There are a lot of experienced terrarium plant experts there. But don't desert us, if you have dart frog questions.
Dendroboard
-----
Patty
Pahsimeroi, Idaho
4 D. auratus blue
6 D. galactonotus pumpkin orange splash back
7 D. imitator
6 D. leucomelas
6 D. pumilio Bastimentos
4 D. fantasticus
6 P. terribilis mint and organe
4 D. reticulatus
4 D. castaneoticus
2 D. azureus
4 P vittatus
2 P. lugubris