Mine send up new shoots/trunks/suckers every year. Native Sambucus Nigra. I tried clearing out the new suckers to leave one big trunk tree; however, I noticed that over time that big tree trunk just gets weaker with less new growth and branches each year. It degenerates naturally and needs those new sucker to form new tree trunks. I've noticed that the canadensis native in our high mountains has similar growth habit. It's really a no worry shrub; they do well in poor soils and even under the plant-killing black walnut tree. I doubt there's a variety that doesn't send new growth from ground/roots.