In article , Andrew G
wrote:

I was always taught that a sucker is a shoot coming from the rootstock.
Just because you have a shoot coming from the base of a plant, that isn't
grafted, and shoot is coming from above ground level, well that would be a
shoot wouldn't it?
Just trying to clarify it in a discussion I had with someone.
They claim that a shoot coming from the base of a maple (not grafted), is a
sucker and it means the tree must be diseased.

My understanding is that a sucker is a shoot coming from any point at
or below the graft. Although damage to the donor plant will tend to
encourage suckers (some will send up suckers from the roots if the main
trunk is cut down, causing a real problem if you are trying to remove a
tree) I have not heard that they signify disease in themselves.

They will draw sustenance from the rootstock more efficiently than the
grafted material and so will eventually come to dominate the plant if
allowed to remain. Luckily, they are usually quite easy to spot. Again,
it is my understanding that it is better to Œrub¹ them off rather than
prune them, to remove all trace and discourage regrowth (but I am
prepared to be corrected!)