Noob OpenGL polygon question

I’m trying to create a tree model using L-system and OpenGL/C++. What I did was instanciating a series of tapered cylinders in a tree shape. I achieved this through popping and pushing into position matrix. But the final product has unpleasant looking joints. I wanna smooth out the connecting joints and make them look less obtrusive. Any ideas would be greatly appreciated.

Hi !

If performance is not important, maybe putting spheres at the end of the cylinders might work.