JavaFX - How to delete a specific Node from an AnchorPane

I'm using SceneBuilder 8.0.0 and JavaFX 8.
I have a Button btn and a Label lbl attached to an AnchorPane ap.
When the application starts, btn and lbl are attached to ap.

How can i delete one of these nodes ? (i only know clear() method which delete all the nodes from ap). thanks.