Does stump killer work, and what does it actually kill?

Does stump killer work?

It works on one job: reducing sprouts from a freshly cut stump. It does not remove the stump. Iowa State Extension says “while herbicides can be used to prevent resprouting, they are not beneficial for promoting decay of the stump.” The stump stays until it rots or someone removes it, for example by stump grinding.

The term “stump killer” covers two different kinds of product, and the sources treat them differently. Fertilizer-type products aim to speed rot. Herbicide-type products aim to stop regrowth. Iowa State says some products contain a herbicide. Read the label to see which kind you have.

What is in commercial stump removal products?

Iowa State Extension says these products “tend to simply be a form of fertilizer (often potassium or sodium nitrates).” It adds that “some of the products will also contain a herbicide, such as triclopyr, glyphosate, or imazapyr, to help prevent resprouting.” Its instruction is to “use these products as directed to prevent damage to nearby plants.” That means the product label.

Illinois Extension names potassium nitrate, also called saltpeter, as a common ingredient and says to follow the label directions. Citing a University of Georgia researcher, it says chemical treatment speeds up decomposition by about 25 percent, while enhancing natural decay can accelerate it by up to 50 percent. See Does Epsom salt rot a stump? for a related claim.

When and how do extension pages say to use herbicide on a stump?

Only while the cut is fresh, and always as the product label says. These steps are as the sources state them. They are not a substitute for the label.

1. Cut the tree or shrub. The treatment goes on a fresh cut surface. Penn State says to use a backpack sprayer, pump-up spray bottle or trigger sprayer, and to mix “according to label directions.”
2. Clean the surface. Iowa State says to “be sure to clean off any sawdust or soil before the application.”
3. Treat the living layer. Iowa State: “Herbicides only need to be applied to the living cambium tissue, which is in a ring just below the bark.” Penn State says for water-soluble products on stumps four inches or larger, treat the living tissue “immediately after cutting.”
4. Pick the right season. Penn State says “treatments in late summer and fall are preferred” and that spring sap flow makes them ineffective. Ohio State’s honeysuckle sheet says late summer, early fall or dormant-season applications have all been effective and to avoid sap flow in spring.
5. Watch for sprouts and retreat. Iowa State says “if sprouts appear after the herbicide application, cut the sprouts and reapply the herbicide,” and to repeat until sprouts stop. Penn State says to “monitor stumps for sign of resprouts after initial treatment, and retreat as necessary.”

The Ohio State sheet is about bush honeysuckle, a woody shrub, not every tree. It still gives a clear statement: “Label recommendations must be followed to maximize the potential for successful control.” See Honeysuckle stumps and roots and How to kill honeysuckle roots. The glossary entry for cut stump treatment explains the method.

Does it work on an old stump or after grinding?

Not as a stump remover. Iowa State Extension says “any herbicide poured into drilled holes or over the stump well after the tree’s removal will only leach into the soil and potentially damage nearby plants.”

After grinding there is no fresh cut to treat, and the hole holds wood chips. If sprouts appear, Purdue Extension (which links them to roots that store energy for the tree) says “simply treat them with typical lawn herbicide as needed at the label recommended rates.” Penn State and Iowa State describe cutting and retreating for repeated sprouts. See Will a stump grow back?.

Is stump killer safe?

Herbicides can harm plants you want to keep, so the label comes first. Iowa State warns against products with picloram (Tordon): “this herbicide easily leaches and remains active in the soil for a long time, causing a lot of collateral damage in the garden.” The Ohio State honeysuckle sheet lists picloram products for woodland honeysuckle, so label rules and site matter. We give no advice beyond the sources. Follow the product label, and for a stump near a tree you want to keep, ask a licensed applicator or an ISA Certified Arborist first.

What other options exist?

Extension sources list several. Iowa State’s page covers grinding, natural decay with drilled holes and fertilizer, digging, and leaving the stump for wildlife. It lists burning as a method to avoid. Read Can you burn a tree stump?, DIY stump removal vs hiring a pro and Stump grinding vs stump removal. The pillar Tree roots, stumps and regrowth ties them together.

Iowa State calls professional grinding “the quickest, easiest, and safest way to remove a tree stump.” The drawback it names is cost. Cincinnati Stump Grinding grinds tree stumps in Dayton, Cincinnati and Northern Kentucky. See Stump grinding cost for reported prices.

Next step

To skip the chemicals and have the stump ground out, see the stump grinding service. Call (513) 587-6772 or send photos for a free estimate.