That's quite a Creeping Mold. Probably reasonable though.

I try my best not to create any "strictly better than" designs, but my thought process in this case is that Creeping Mold existed pre-Planeswalker. That it also has Melody? Well, it could perhaps use an additional colorless mana.

Creeping Mold was always playable, but never exciting. Like Break Asunder. This kind of effect at 5 mana is Rootgrapple, which was an instant and conditional cantrip. This is a conditional double-cantrip, so I guess perhaps it should be 5 mana as well, even though that does feel dispiritingly expensive.

It would seem precedent suggests that this is fine in theory. Only playtesting can discern whether the cost or effect might need changing.