A stump ground below grade almost never grows back, because the part of the tree that sprouts is gone. The roots left in the ground die and rot over several years, though a few species, such as black locust, sweetgum and tree-of-heaven, can send up shoots from those roots for a while.
The short answer
There are two different things people mean by 'grow back'. One is the stump itself sprouting, the ring of shoots you see around a hardwood stump the spring after it was cut. Grinding below grade ends that in nearly every case. The other is shoots coming up out of the lawn some feet away from where the tree stood. Those come from roots, not the stump, and only certain trees do it. If you know which tree you had, you can tell in advance which of the two to expect, and for most trees the answer is neither.
Why a cut stump sprouts
A stump that is cut and left is often still alive. Penn State Extension explains that stump sprouts come from dormant buds held at the root collar, the place where trunk meets roots, and that hardwoods in general are able to do it while conifers rarely do. Red maple is a prolific sprouter. Tulip poplar comes back so readily that NC State Extension notes it can be cut to the ground again and again. Oaks, sweetgum, Bradford pear and crape myrtle all do it. In some species, older and larger trees are less likely to sprout than young ones. A sprouting stump is not a new tree yet, but give it a few summers and it is a thicket.
Why grinding below grade stops it
Grinding removes the part that sprouts. The root collar and its buds sit at and just under ground level, and a grind that goes four to eight inches below grade and out across the root flare turns all of it to chips. What remains is roots with no trunk, no leaves and no way to feed themselves. That is why regrowth from a properly ground stump is rare, and why a stump only shaved level with the lawn can come back. If a tree you had cut is already sprouting, stump grinding deals with the stump and the shoots in one pass.
Which trees sucker from the roots
A short list of trees can make new shoots from roots alone. Black locust is the classic one here: NC State Extension describes it sending out long underground root suckers, and calls it a native forest tree in the North Carolina mountains. Sweetgum is another, and Forest Service research records dozens of sprouts rising from the root system of a single tree. Tree-of-heaven is the worst. Penn State Extension says a cut tree may send up dozens of stump and root sprouts, and that root suckers can come up as far as fifty feet from the parent tree. Clemson Extension lists root sprouts as one way Callery pear, the wild form of Bradford pear, spreads. Tulip poplar is mainly a stump sprouter, so grinding the stump deals with it.
Pines and other conifers
Most conifers do not come back from a stump at all. Penn State Extension notes that gymnosperms rarely sprout, and that the few pines able to, such as pitch and shortleaf, lose the knack with age. In practical terms, the stump of a mature loblolly or white pine is dead wood the day the tree comes down. That makes pine stumps simple: no ring of shoots next spring, no suckers in the lawn, and softer wood that grinds faster than oak. The reasons to grind one are the usual ones. It is in the way, it is ugly, or it is where the mower goes.
What to do about suckers
Cut them off low or mow them, and keep at it. A sucker lives on energy stored in the old roots until it has leaves enough to feed them back. University of Maryland Extension advises that prompt, repeated removal will in time exhaust those reserves, and that letting shoots grow before cutting just refills the tank. In a lawn, ordinary mowing does this for you, though it can take a while. Beds are slower because nobody mows them, so clip shoots as they show. For stubborn species such as tree-of-heaven, your county Extension office can advise on herbicide use and timing. Follow the product label exactly.
What happens to the roots after stump grinding
They stay in the ground, die and rot. Cut off from the leaves, roots have nothing coming in, and soil fungi move into the wood. Purdue Extension says full breakdown can take several years. Fine roots vanish first and the thick ones near the stump last longest. As they go they leave small voids, so the surface can dip along a root line, and Iowa State University Extension notes this can make turf uneven later. Mushrooms in wet weather are the same process showing above ground. Dead roots do not keep growing and do not go looking for pipes or foundations. What to do after stump grinding covers the upkeep.
When the roots have to come out
Roots rotting under a lawn are no trouble. They are trouble under a slab, a footing, a post or a new tree, where settling or crowding matters. In those cases the answer is not a deeper grind. It is full stump removal, where the excavator or loader lifts the root ball out whole and the hole is backfilled. A storm-thrown tree is the other case: a root plate tipped up on edge has to be lifted out, since there is nothing flat left to grind. Stump grinding vs stump removal sets the two jobs side by side.
Common Questions
Will a tree grow back if I grind its stump?
Almost never from the stump, once it is ground below grade, because the buds that sprout sit at the root collar and that is turned to chips. A few species, black locust, sweetgum and tree-of-heaven among them, can push shoots up from roots farther out. Mow or cut those low and they give up as the roots run out of stored energy.
How long does it take for tree roots to decompose after stump grinding?
Years, not months. Purdue Extension puts full breakdown of the buried wood at several years, and it varies with the tree, the size of the roots and how damp the soil stays. Small roots are gone first. The thick roots of a large hardwood last longest. Nothing needs doing to them in a lawn beyond topping up any dip that forms.
Should I remove tree roots after grinding a stump?
Under a lawn, mulch or a natural area, no. They rot where they lie and digging them out tears up far more yard than it saves. Take them out when a footing, slab, post, drain or pool is going in that spot, or a new tree in the very same place. That is a removal job and worth saying at the quote.
What to Do Next
Know what tree it was? Say so when you send your two photos, along with your town, and you will be told whether to expect shoots and whether grinding or removal fits. Call (828) 574-4474.