The most beautiful thing (a cactus (obviously)) can now be endlessly shown in front of your face.
I feel like you went through necessary work, is there a reverse function for strings in Python? If so, it would've used a single variable.
Also, the loop constantly joins the arrays, you could've done this:
cactus2 = "\n".join([ ..., ... ])
Now it just sets the variable and reads from it.