I think it is hard to beat eucryphias as evergreen trees that flower in
that awkward late summer period of mid-August-September and two in particular are my choices. The other is Eucryphia 'Nymans' a very upright showy tree (love it) but I have a strong affection for 'Rostrevor' that has a much looser slightly weeping form, again covered in flowers in late summer. They need an acid soil though I am afraid. If you have that you have to have this, a must have.