You could try flying over and under it deftly after luring it to the surface. (Shoot at it or something while you're ascending a tunnel you made right above the bulb)
We tried luring Plantera to the surface, but we had difficulty with one of us either getting trapped while trying to escape, or getting too far away from Plantera at any one point.
And if you rooster-up then you'll have to dig another tunnel down to your new bulb. I found it easier to move underground heading downwards instead of upwards, so it was easier for us to get to the dungeon wherever we were.
But it might just depend on what your Jungle looks like. Ours was pretty tight and twisted near our entrance, but was open down near the dungeon, letting us get there easily.
The bonus of making a path around the Dungeon though is that you can make the path tight enough for you to move in, meaning Plantera can't always get close and attack you with it's head. So if you have a lance weapon then you can damage plantera while they're in the walls.
We took a few tries to finally take out Plantera, but once we did it we got really comfortable with it, and have been able to take out Plantera really quickly each time afterwards.
