Grafts are only successful if the grafting partners are related to each other. So in most cases, grafting members of the same species is most successful, followed by success between partners in the same genus. There is limited success among family members.
In some cases, the graft is initially successful but then begins to fail. This failure may be due to an adverse physiological response between partners; virus; or anatomical abnormalities.
Delayed incompatibility can occur between some graft partners after years of growth. In these cases, the graft union may function for 10 or more years before failing.
As seen in the maple to the right, only a portion of the graft union (arrow) appears to have formed well. Eventually, the weight of the canopy and a brisk wind was sufficient to snap this large tree at the graft.
Delayed incompatibility can be seen in red maple, various oaks, ash and some conifers.