If allowed to grow unchecked past year 3 an elderberry plant can become what some.
Pruning Tips During the first two seasons, elderberry plants should be encouraged to grow vigorously with little to no pruning required. After the second year, pruning should be done annually in early spring. All dead, broken and weak canes should be removed. As the plant matures, some “renewal pruning” should be done. This is done in early spring by removing two or three of the plants largest canes to the ground.
Repeat this process each year over a three year period to re-invigorate old plants. Please be aware, however, that renewal pruning will reduce the number of blooms for that year.