Every other type of sapling behaves normally, but these saplings specifically do not grow under conditions that should otherwise be perfectly valid.

Redwood, fir, and umbran saplings refuse to grow when there's vegetation within one block that happens to be on a positive axis relative to the sapling.
Palm saplings refuse to grow when there's vegetation within one block of the sapling at all, regardless of relative position.

Additionally, while 3x3 redwood trees can be found naturally generated, there appears to be no way to create one yourself.