Graphics environment is still forced to be headless under Mac.

Sample (just to illustrate problem):

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;


import com.sun.javafx.application.PlatformImpl;
import javafx.scene.Scene;
import javafx.embed.swing.JFXPanel;

import javafx.scene.control.Button;
import javafx.scene.layout.VBox;

public class Main {

    private JFXPanel javafxPanel;
    private Scene scene;

    public Main() {
        JFrame frame = new JFrame("Swing interop");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        javafxPanel = new JFXPanel();
        javafxPanel.setPreferredSize(new Dimension(550, 400));
        frame.getContentPane().add(javafxPanel, BorderLayout.CENTER);
        createScene();

        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private void createScene() {
        PlatformImpl.startup(new Runnable() {

            public void run() {
                VBox root = new VBox();
                scene = new Scene(root);
                root.getChildren().add(new Button("FXButton"));
                javafxPanel.setScene(scene);
            }
        });
    }


    public static void main(String[] args) {
        Button btn = new Button("");
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Main();
            }
        });
    }
}