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Using Epsom salts to kill aspen stumps? #662103

Asked July 09, 2020, 5:23 PM EDT

I live in Denver, and have five 10"-diameter aspens in my front garden that have reached their use-by date. I want to cut them down and then get rid of as much of the stumps, roots, and myriad tiny clone trees as possible. The arborists that I've contacted propose: cut down the trees, drill the stumps, add Garlon/triclopyr, then wait 6 months and grind down the stump to about 6" below ground level. I'd really like to avoid using such a high-power herbicide, especially since I have three evergreens in the yard, and don't want to risk killing them as well (via communication through roots?).  Looking for an alternative, I've found numerous websites that say I can kill a tree stump by drilling several 1" holes, filling them with Epsom salts (magnesium sulfate), moistening with water, and covering with a tarp. Supposedly, the Epsom salts draw moisture from the stump and soil, and after a couple months (replenishing the salts as needed), the stump dies and can be dug or ground out. Here's a particularly complete description: https://mrtreeservices.com/blog/how-does-epsom-salt-work-on-tree-stumps/  This approach seems almost too perfect in its ease and environmental friendliness.  Does it work, and specifically does it work on aspen?  My yard has no grass and, in addition to the trees, is planted in shrubs, perennials, and a boatload of feral oregano; everything is watered on a combination of driplines and sprinklers.  To further stress the aspens, should I wait until the water is turned off for the winter?  I'd greatly appreciate your input.  Thanks!



Denver County Colorado

Expert Response

 Aspen have the ability to sprout profusely from their root systems to produce a new forest, especially when the main tree is cut down. This is good for aspen, giving it the ability to reproduce and populate an area quickly after a disturbance such as a fire or avalanche. It is not so convenient for homeowners growing aspens in a cultivated landscape, since the trees shoot out multiple sprouts when cut down.  

I could find no university based research that would support the claim that Epsom salts are effective in removing tree stumps. There are many gardening practices that have no scientific basis yet continue to appear in blogs or other unscientific internet sources. This is probably one of them. Epsom salts is a chemical comprised only of magnesium and sulfate. Plants use trace amounts of both sulphur and magnesium. Both of these minerals are already found naturally in the soil. As you noted, if it seems too perfect to be true, it probably isn't!  

The part about covering the stumps with a tarp might be partially effective because decreasing the light intensity inhibits new root development and stem growth. I suppose there is no harm in trying the Epsom salts method, but I found another person's question in our archives who "tried loading cuts in the stump with Epsom salt and adding water to try to kill the stump and roots" and the suckers were "still coming up relentlessly."  
 
When cutting down an aspen tree, it is necessary to kill the entire root system connected with the original tree. As long as the root system is alive, it will continue sending up sprouts. It may take up to two years of cutting and treating sprouts to completely remove them. The tree company you spoke to may have offered the fastest solution to getting rid of your stumps.  

Here are some considerations:
           
The herbicides Brush-B-Gone or Glyphosate (RoundUp) or an equivalent with the chemical triclopyr are well suited for this task and available at most garden centers. This works best on a freshly-cut stump. Spray the herbicide on the cut ends or on any leafy sprouts that appear. You could also paint the chemical on the cut ends or leaves with a small brush or foam brush to minimize it drifting to any other plants. Because aspen are an interconnected series of roots and shoots, the herbicide can travel through the roots of all the aspen. It should not, however, travel to the roots of any other trees such as your evergreens. If applied properly in strict compliance with the instructions on the label, it would not enter the soil and would have no influence on other plants.  

* Products containing 2,4-D (Weed-B-Gone) can be absorbed by the roots of other desirable plants. Products containing glyphosate (RoundUp) cannot be absorbed from the soil but can harm other plants if applied on a windy day.

The chemical translocates into the roots, reducing the ability of the roots to produce sprouts. You will likely continue to have sprouts for sometime, and you should treat them as soon as you see them. It is best to cut and treat them before they have much time to grow. If the trees aren't treated right away, the downward movement of material within the trunk (translocation) has ceased and the chemicals may not be effective on the stump.  

You can also drill holes in the stump with a large drill bit, then fill the holes with undiluted brush killer. You will probably still get a few suckers still coming up, but if you remove them - and treat with brush killer they will come up less and less frequently. The stump will eventually rot, but could take a few years.  
 
 In place of chemicals, you may apply some old-fashioned elbow grease and remove the sprouts by digging them up or mowing them. Digging them up a few inches below the ground level will be sufficient and better than just mowing. You will not need to dig several feet down - just cut below the soil line. In either case (using chemicals or mechanical removal), the object is to deplete the stored food reserves in the roots system by removing new growth after it draws upon the stored food but before it begins to return food to the roots.  Without leaves to produce food, the root system will eventually die, so effort should be focused on the timely removal of any shoots that grow. Shoots that form all along the root system should be removed promptly. Over time, the dead roots will rot.

Here are links to some articles that I relied upon and that may help you get rid of your stumps:  


Thank you for your inquiry and best of luck with your aspen removal.  
An Ask Extension Expert Replied July 10, 2020, 9:42 AM EDT

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