Adding root node to an existing TreeView C#

Guys i am having a problem adding root node in a Treeview. Code is running nice but i want to add one Parent root as "My Root". Currently there is no Parent root displaying. I have the code given below:

private void PopulateTreeView()
    {
        treeView.Nodes.Clear();
        ////set root node of TreeView.
        treeView.ImageList = imageList1; //connect tree to image list


        SqlDataAdapter da = new SqlDataAdapter("SELECT pID,pDate,pName FROM table1 order by pName", con);
        SqlDataAdapter daCategories = new SqlDataAdapter("Select * from table2", con);

        DataSet ds = new DataSet();
        da.Fill(ds, "table1");
        daCategories.Fill(ds, "table2");

        //TreeNode root = new TreeNode("My Root");
        //treeView.Nodes.Add(root);

        ds.Relations.Add("Dept_SubDept", ds.Tables["table2"].Columns["pDate"], ds.Tables["table1"].Columns["pDate"]);
        foreach (DataRow dr in ds.Tables["table2"].Rows)
        {
            DateTime dt = Convert.ToDateTime(dr["pDate"]);
            TreeNode tn = new TreeNode(String.Format("{0:dd-MMM-yyyy}", dt));

            foreach (DataRow drChild in dr.GetChildRows("Dt_Pat"))
            {
                tn.ImageIndex = 0;
                tn.NodeFont = new Font("Segoe UI", 10, FontStyle.Bold);
                treePatient.Indent = 10;
                TreeNode childTn = new TreeNode(drChild["pName"].ToString());
                childTn.Tag = drChild["pId"];
                tn.Nodes.Add(childTn);
            }

            treeView.Nodes.Add(tn);
 }
}
Please help me. Thanks in advance.

Apurba