Planting Medium

Simple question, I trust:

If I have an undergravel, and am trying to keep plants like,
some sort of sword
hygro (presumably polysperma)
java fern

what should I plant these in?  In other words, should I just stick them in
the gravel?  Should I be potting them?  I gather I should avoid the plugs
which I gather are augmenting my algae problem.