Nudging the cacti - A5 vertical room

So the only thing I can think of at this point is to run back and forth into the key about 1000 times to nudge the cactus into the spike wall, and then do the same thing once I've gotten up top to push the other one out of the way. But that doesn't seem quite right... am I missing something obvious here?

Then, if your stuck after that:

Huh. And I thought you needed to use to get yourself up there. Thanks!