To reproduce run following code



import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class TreeViewBorder extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    private Parent getContent() {

        VBox list = new VBox();
        TreeItem<String> root = new TreeItem<String>("ROOT", new Rectangle(20, 20, Color.CHOCOLATE));
        TreeView tree = new TreeView(root);
        tree.setFocusTraversable(false);
        tree.setStyle("-fx-border-style: segments(5,10); -fx-border-color: red;");
// tree.maxHeight(50);
// tree.maxWidth(50);

        list.getChildren().addAll(tree);
        return list;
    }

    public void start(Stage stage) {
        stage.setX(100);
        stage.setY(100);
        stage.setWidth(500);
        stage.setHeight(500);
        Scene scene = new Scene(getContent());
        stage.setScene(scene);
        stage.setVisible(true);
    }
}