Gotta Really Think!

Riddle: My stem's planted firmly where I am allotted. My tail is wavy and my face is quite blotted. I relay much emotion though flatly I'm spotted, And I grow half my size whenever I'm dotted. I can speak any language, yet utter no words. I'm no seed, yet I am well known among birds. But I do have a speech impediment: I can say cage but not page, aged but not wage. What am I?