Whose a sucker?
You may have noticed that an odd branch has started growing from the base or the roots of your tree. It may look much like the rest of the plant, but soon it becomes apparent that this strange branch is nothing at all like the tree you planted. The leaves may look different, it may produce inferior fruit or it may be a different kind of tree all together. What is going on? Your tree has developed a sucker. What is a Plant Sucker? You are probably thinking, “What is a plant sucker?” Essentially, a plant sucker is an effort by the tree to grow more branches, especially if the tree is under stress, but you have taken perfect care of your plant and it wasn’t under any stress. Besides, that does not explain why your tree has suddenly switched varieties. Chances are, your tree is actually two trees spliced or grafted together. With many ornamental or fruiting trees, the desirable tree, for instance a key lime, is grafted onto the rootstock of an inferior but hardier related variety. The top of the tree is perfectly happy, but the lower half of the tree is under a certain amount of stress and biologically will try to reproduce itself. It does this by growing suckers from the root or lower stem. Tree suckers can also grow on non-grafted trees, but are most common on grafted ones. This explains what is a plant sucker.
Read more at Gardening Know How: Tree Sucker Removal And Tree Sucker Control https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-sucker-removal-and-tree-sucker-control.htm