Barbry Allen was buried in the old churchyard
Sweet William was buried beside her
Out of Sweet William's heart there grew a rose
Out of Barbary Allen's a briar
They grew and grew in the old churchyard
til they could grow no higher
At the end they formed a true lover's knot
and the rose grew round the briar.

OK, they still had to grow out of the coffins and up thru the ground, but then true love is an amazing thing!