Um, if you can't climb straight up, you don't go!  

Vx is a speed, not a chart to tell you that you can clear an obstacle!  

You might not be able to climb at zero airspeed, but can at some airspeed above zero, or don't you remember that from flight school?   When you hit LTE, suddenly, you have lots of lift and can climb far better than you can at zero airspeed.

Maybe your too young to remember that technique getting out of a tight LZ.

Vx is the best climb gradient speed for a distance over the ground.

Vtoss is the minimum speed that give you a climb (not necessarily the best for a given distance).

Vy is the best rate in a given amount of time.