It's easy enough to find out.

First, poke your finger down from the top.
Do you feel dirt, or roots?

Next, look at the drainage holes.
Any escapees?
No can tell?

Let 'er dry out a li'l bit, lay the bucket on it's side and roll it back n forth a couple times.
That should loosen it.
Then put down a plastic bag and gently pull on the stalk, to slide the rootball out for a look.
If you see solid roots, it's time.

Looks like you have enough head room to "stack" it.
When they are tall, but not wide, they respond to stacking very well.
Drill a few 1" holes in the bottom of the bucket and set it on top of another bucket filled with fresh medium.
No mess, no stress.

Hope you sexed it before you started, because "it look a like a man" to me.
I'm just sayin'...

Aloha,
Weezard