I just planted a bunch of these on a stream restoration project. Both are very easy to establish (given the proper habitat) from cuttings or thicker branch pieces known as live stakes. I've created some very nice marginal fish habitats with buttonbush - they will easily grow in up to three feet of water. Silky dogwood is not as adapted to standing water, or even permanently saturated soil - it prefers seasoanlly saturated soils further up from water's edge. Both are great wildlife plants with attractive flowers and valuable fruits. Buttonbush is by far one of my favorite shrubs - the flowers are very unusual and the older plants have a very nice gnarly structure about them.