Q.propagation from suckers
I propagate elderberries for local game depts. I have an abundance of spring suckers/roots that I have had to dig out. In the past, I have had very little success with spring suckers. I have about 100 now in water, but need to know the best way to deal with them.

Propagation of Elderberries should be from soft cuttings.
Here is a link that will help you.
https://www.gardeningknowhow.com/edible/fruits/elderberry/rooting-elderberry-cuttings.htm