It actually comes from both, however it originates from the clouds where a negative charge is built followed by a strike on a positive charge on the ground.
Does Lightning Come From The Ground
Lightning streaks inside a cloud, between clouds, and from clouds to the ground. Lightning is a flow of electrons (a negative charge) that zigzags downward in a forked shaped pattern (scientists call this a step leader). As it nears the earth, a stream of positive charges moves up to the charge of electrons (negative charge). When they meet, the power flows. We can't see this because it moves too fast (first stroke). The return flow (positive charge) moves upward more slowly. This is what we see and call lightning (return stroke). If there is a flicker, the upward stroke is repeating the process.
That lighting bolt you see has been proven to go from the ground up.
The US government is doing test very close to my house by the Lakeland, Florida airport!
This area is by far the most lighting strikes in the US. So they are trying to relieve the force by shooting small rockets into the thunderstorm clouds, with a grounded wire attached to it, and thereby causing a controlled bolt of lightning to strike down that wire.
This proves my answer!
The US government is doing test very close to my house by the Lakeland, Florida airport!
This area is by far the most lighting strikes in the US. So they are trying to relieve the force by shooting small rockets into the thunderstorm clouds, with a grounded wire attached to it, and thereby causing a controlled bolt of lightning to strike down that wire.
This proves my answer!