How to Propagate flowering dogwood 'Rainbow'?
Propagate by softwood cuttings in summer

flowering dogwood 'Rainbow' · Cornus florida 'Rainbow'
Grow in fertile, well-drained, neutral to acid soil in sun or partial shade. Keep roots cool with a mulch in summer. Shelter in exposed locations. For more advice, see flowering dogwood cultivation
Propagate by softwood cuttings in summer