Hello,

While the Sweetgum tree ( Liquidambar Styraciflua) has many good qualities, they are well known for their shallow root system and can lift roads and sidewalks. For residential properties, these trees can cause the problems that you are experiencing. Unless they are at least 10 feet away from roads, building and pavement, they will cause problems with plumbing.

Your arborist suggested poisoning the stump to prevent continuing root growth. That presupposes that you do not have the stump ground out. The first thing I would suggest is having the same company cut down the trees and grind out the stumps. Stump grinders remove remaining parts of dead or freshly cut trees. Because surface roots of a sweetgum tree develop during maturity, sweetgum trees may grow too large for non-professional use of a stump grinder. Call a professional for stump and root removal if you do not have experience in the use of stump grinders or if the sweetgum tree is too large for successful removal with a small grinder. If a professional tree service was used, they will leave a big pile of wood chips. You can rent a stump grinder, but they're expensive and can be dangerous if you don't know what you're doing.

Having your tree removal service grind the stump is not the least expensive method, but it is the quickest. There are several other methods that you can use for stump removal beside grinding to do this. Whichever you choose is up to you. But, do this first.

Severing the Roots

Sweetgum trees develop surface roots as they mature and severing one major root within a small diameter of the trunk may kill up to 25 percent of the tree’s root system. Surface roots of the sweetgum tree damage hardscape features in your landscape, such as sidewalks, driveways and porches. Their aggressively spreading roots may connect to nearby trees, causing a union in their vascular systems and using herbicides on sweetgum trees that have shared vascular systems may potentially damage desirable trees when the herbicides travel through the sweetgum tree’s roots. Measure the sweetgum tree and mark it at one-foot above ground level. Cut the tree down to the mark and drive a sharp spade into the ground surrounding the stump to sever the roots away from possible vascular connections.

Here are other ways to remove the stump beside grinding. These require patience and in some cases a lot of energy on your part.

Manual Removal

Tools: chain saw, axe, mattock, shovel

Manual tree stump removal uses a hefty mattock. Its broad end allows you to dig around the stump; the other end functions as an axe for chopping your way through tree roots. Dig and chop your way under the root ball to the taproot. For large tree stump removal, taproots may be imposing enough to require cutting with a full-size axe. This method takes time and a bit of endurance. All you're trying to do is remove the central mass of the stump and not all the main roots that spread out through the ground.

Alternative removal technique: Using Fertilizer

Tools: drill, large drill bit, high nitrogen fertilizer, heavy plastic (tarp), mulch.

Wood that isn't alive will eventually rot from moisture, insect activity and natural microbes, but depending on the original wood, may take several years to accomplish. This alternative removal method is essentially one way to hasten the natural processes. It doesn't work over night, but within a year, with any luck, you'll have reduced the massive tree trunk to a soft pulp that you can just ignore, or safely remove it with the mattock and shovel.

To speed up the natural process you’ll be adding 2 ingredients in unnatural quantities that when combined will speed up the decaying process. Those ingredients are nitrogen and water.

Make sure the stump is cut down as close to the ground as possible. Once the stump is leveled off, drill some holes at least 2" deep or more, into the stump in several places, using your widest drill bit. The more, deeper and wider the holes are, the better.

Fill the holes with water, then comes the fertilizer which should be high in nitrogen. If using a commercial fertilizer, make sure the first number on the bag is the highest. Pour this fertilizer into the holes. Next, soak the ground evenly around the stump.

Cover the stump with a plastic tarp, either black or clear, since it will be covered over with a sheet of plastic. The tarp acts as a barrier that will help keep the area and the wood moist. Cover the plastic with an organic mulch and dampen it thoroughly. Any organic mulch will do, such as wood chips or shredded bark. This mulch will help hold in additional moisture keeping the area even wetter. Wet mulch will keep the tarp in place. If you have a few large stones available, roll them onto the tarp.

The final step is patience. The above steps greatly speed up the natural rotting process, but it will still take some time. Then sit back and wait for completion of your tree stump removal project.

Periodically repeat the process: remove the mulch, plastic and add more nitrogen, then re-apply the plastic and mulch. Soak the mulch again, too, to keep the tarp wet and weighed down.

Another way to get rid of the stump is to use a homemade weed killer, such as vinegar or rock salt, to destroy the stump and kill the roots. Another is to turn the stump into a compost pile or flower container to speed up decomposition.

Vinegar can be an herbicide both organic and effective, although multiple applications are necessary to kill the roots. Select a warm, dry day and fill a spray bottle with undiluted white vinegar. Spray vinegar to thoroughly coat the leaves of shoots growing back from the tree roots and stump. This destroys the leafy top growth that is supplying the roots with food and eventually kills the remaining tree roots.

Salting your tree stumps with rock salt acts as a weed killer by absorbing water that would normally be used by plant roots, resulting in drought like conditions. When the salt is dissolved by water, it can be absorbed by the tree roots and build up to toxic levels. Care should be taken when deciding where to sprinkle salt on the soil around a tree because it will kill grass and desirable plants as well. To target the tree stump specifically, drill 12-inch-deep holes in the stump using a 1-inch spade bit extension. Pack these holes with rock salt.

Depending on where the trees are, one way to get rid of an unwanted stump is to build a homemade compost pile on top. The compost pile will speed the decay of the stump.

Killing tree stumps with Epsom salts (magnesium sulphate) is a readily available, cheap and completely safe method for people and the environment. Large amounts of Epsom salts will draw moisture out of a stump much like an over-application of fertilizer does to roots, eventually drying it out, after which it will just naturally rot away. Any magnesium released into the soil will just be taken up by plants – magnesium is the key element in chlorophyll which allows plants to photosynthesize and makes leaves green.

Procedure for killing a tree stump with Epsom salts:

1. Drill holes into the top of the tree stump, using a 25mm (1”) drill bit. Drill holes at least 15-20cm (6-8”) deep using a spade bit or auger bit. On larger stumps, space the holes around 7-10cm (3-4”) from the bark edge and from each other. On smaller tree stumps aim for six or more holes. The intention is to create enough holes that run deep enough to hold an enough Epsom salts so that it can more easily penetrate the wood and the roots to dry them out.
2. Fill all the holes with dry Epsom salts all the way to the top.
3. Slowly add just enough water to each hole to moisten the Epsom salts – it doesn’t need to be really wet, just moist, and be careful to not wash the Epsom salts out of the holes.
4. To prevent the Epsom salts being washed out by rain, cover the stump a sheet of plastic, a garbage bag or a tarp, and anchor or fasten down the cover so it doesn’t get blown away by the wind.

If roots extend from the side of the stump, they too can be drilled and filled with Epsom salts. If the stump if freshly cut, once it is drilled and the holes are filled with Epsom salts, the whole surface of the stump can also be cover with a thick layer of Epsom salts to speed up the drying process.

The stump can take up to six months to dry out, depending on the size of the tree and its root system. Check the stump each month to see if the level of the Epsom salts in the holes has dropped as it’s been absorbed. If it has, top up the level of the Epsom salts and moisten as before.

Hopefully you won’t have to kill too many more trees in your yard, but if you do have to remove a tree, this is definitely a much better way to get rid of living tree stumps than contaminating a garden with poisonous chemicals!

If, after all of this you choose to use a herbicide, please go to this URL: https://edis.ifas.ufl.edu/publication/ag245

Remember to follow all the directions on the package and protect yourself. Before mixing herbicides, wear safety equipment, such as goggles, work gloves and long sleeves.

I hope this is helpful.