Manitoba maple (Acer negundo), also called boxelder, is common in Southern Ontario. The species is not automatically dangerous, but mature specimens often develop structural features that deserve attention around homes and occupied areas.
Why can Manitoba maples fail?
They can develop fast-growing, spreading crowns with several large stems. Large competing stems, storm damage, decay and weak unions can combine to increase failure potential.
Co-dominant stems and included bark
When two large stems grow from the same union, bark can become trapped between them instead of forming a stronger wood connection. These unions deserve particular attention as stems become larger and heavier.
Warning signs
Fresh cracks, movement at a union, large dead limbs, cavities, fungal fruiting bodies, root-plate movement, storm damage or a recent change in lean are reasons to have the tree assessed.
Should every Manitoba maple be removed?
No. The individual tree matters. Management can include monitoring, selective pruning, support systems in suitable cases, or removal when risk cannot reasonably be reduced.