The Ivy (NaPoWriMo 26)

I creep,
Unnoticed,
Up the side of your house and gate.
Day by day, I climb higher.
My many green hands
Reach onto whatever they can to support my body.
I am a greedy monster.
Whatever I can reach,
I claim, whether it be a tree,
Or a fence.
Even though I spread quickly,
You do not see me until it is too late.
My leafy limbs spread everywhere across a yard,
Devouring other opponents.
I steal their health,
And leave them to wither away
To turn to dust and blow away in the wind.
Yet I wait and watch
For the time where I may rule the earth.
That day will be great:
No more legs will I lose to the humans,
For they will not exist.
What am I?
I am the Ivy,
And the Ivy is...
UNSTOPPABLE.