I am redoing by back garden and in the sunny corner at the far end of
the garden (garden is only 40 feet long) I will have a bench across
the corner of the right-angle formed by two fences meeting.

I would like to plant a tree there that will eventually overhang the
bench and give dabbled shade, be interesting to look at, etc.

Prunus serrula has great bark and I believe that if I buy a single
trunked specimen I can then cut it back to about 1 foot of the graft,
seal and it will shoot multiple trunks - is this correct (I would
ideally like three or four like silver birches tend to have).

However whilst reading up on the prunus I came across the Styrax.
This seems to have equally interesting bark, scented flowers, etc.

I don't want anything to get too large (in my time at the house) - so
under 20 feet I would think. Also if it grows so that it is 16 feet
of trunk and then 4 of foliage that is no good either.

Any advice would be gratefully received.

regards

Ed