Tree with Entity Framework

Question

I have a simple structure like this

class Host{
   Node RootNode;
}
class Node{
   Node Parent;
   Children ICollection<Node>Children;
}

And I have the model builder as

modelBuilder.Entity<Node>()
    .HasOptional(x => x.Parent)
    .WithMany(y => y.Children)
    .Map(m => m.MapKey("Parent_Id")).WillCascadeOnDelete(false);

However, when I query I do not get the whole tree but just the first child. How can I get the whole tree data loaded. Here is the query.

return db.Host
         .Include(l => l.RootNode)