If they are growing larger, that is good. Do as Biulu says. Keep them ontop until they sprout then plant them.
While the Blyxia is very healthy and pretty, the positioning right on either side of the wood makes me feel that I'm entering a front door, especially since there is a cave in the wood. I don't know, seems kind of symmetrical to me. It doesn't look bad, it just looks kind of "obvious", if you catch my meaning. Maybe the hairgrass can be redistributed to soften that effect. If you like it, then by all means, keep it that way. I'm only offering a suggestion. It doesn't look random to me, it looks placed. Good scapes, IMO, should look like the plants would just grow there if left to their own devices. Probably not to everyone's taste, though, so I leave it up to you. Otherwise, this is really coming along. Very healthy and lush.