Trees
High
High (>$5000/gross)
Moderate–high risk
Moderate–high risk
Moderate risk
Moderate (erosion, wildlife, habitat)
Overview
Stump grinding removes trees and large shrubs by chipping them to below ground level using a power tool with a high-speed, steel-toothed cutting wheel. Grinding is a way to control individual trees and thick-stemmed shrubs that otherwise resprout when cut. Grinding is not a control method on its own, as it requires removal of above ground biomass first.
Cutting wheels are either vertical or, less commonly, horizontal. Grinders are gas-powered machines that come in many shapes and sizes. They can be walk-behind units that a worker rolls into position, dedicated drivable machines, or attachments to large equipment (e.g., backhoes). The most commonly used stump grinders are walk-behind and are usually available at big box hardware stores to rent. Stump grinding is generally less expensive and labor intensive than stump extraction, but still very costly and potentially disruptive to surrounding habitat and structures.
Control typically requires only a single visit to grind down targeted mature plants. Trunks must be cut down to ground level prior to grinding and the stumps must be ground to below ground level in order for this technique to be effective. Grinding only targets the mature life stage of a woody plant and typically cannot be used economically or effectively on small trees or shrubs with trunks less than several inches in diameter.
Grinding will leave behind an excavated hole of wood chips and dirt as well as well as aboveground biomass from cutting. Site considerations may require remediation and biomass removal. The grindings that remain may suppress passive revegetation.
This technique can be used to eradicate a species at a small scale if plants are mature and at very low density. Limitations include site access and grade requirements, habitat disruption, cost, and operator safety.
How to Use
Stump grinding requires a skilled operator and many safety precautions. Before employing this technique, an operator must read and understand the entire manual for the grinder being used, get sufficient training to operate the equipment safely, and have appropriate personal protective equipment (PPE). Grinders available for rent are typically 25 hp and have a 16” cutting wheel. Transporting a grinder requires a vehicle rated to haul the machine’s weight and a trailer hitch. Alternatively, tree service providers can be contracted to do the work. A single tree will cost $100 – several hundred dollars to grind.
Prepare the stump by removing all rocks from around its base. Trim the stump to be as flush to the ground as possible. When using a traditional grinder with a vertical wheel, raise the wheel over the front edge of the stump, start the wheel spinning and lower it into the stump to grind away no more than three inches (unless stated otherwise in the grinder’s manual) of material at a time to avoid bogging down the engine. Swing the blade back and forth across the stump, grinding down wood as you go. Repeat this process until the hole is at least 4” below ground level to prevent resprouting. Fill the hole with soil and wood chips. Process aboveground cut biomass according to site needs.
Moderate slopes can be accessed from an adjacent stable, flat surface using a backhoe or similar equipment with a grinding attachment on an arm extension. Grinding to below ground level may be difficult on slopes because the grinder will be more difficult to position optimally.
Large, specialized vertical stump grinders are also occasionally employed for high intensity vegetation management, but their utility for wildland weed control is limited because of their size, cost, and destructiveness to surrounding vegetation.
The following links provide step by step instructions and illustrations:
https://www.popularmechanics.com/home/lawn-garden/how-to/a129/stump-grinder-tips/
https://www.youtube.com/watch?v=GspnPRorkEM
Special Tips
Be sure to remove any rocks at the base of the stump. Rocks will dull cutter heads quickly. Chips can fly far and potential break windows or hurt people adjacent to your work area. You may need to put up barriers made of plywood or other material to stop flying chips.
Optimal Conditions for Use
Grinding requires a highly accessible site (or specialized equipment that can reach the site from an adjacent location that is accessible).
If the goal is to fully control a given species, grinding is most effective on target species that are not actively recruiting or when combined with methods to address by also removing younger individuals of the species using other methods.
Caveats
- This technique only targets mature forms of large woody plants and therefore should be either focused where recruitment is not occurring or combined with another method that can address young plants/seedlings.
- Heavy equipment should not be used on wet or muddy soil because it will compact soil.
- This technique is expensive and limited to accessible sites that are not steep.
Some trees, such as Acacia, Mayten and Tree of Heaven resprout vigorously from extensive lateral roots. Stump grinding may not be effective for these difficult species.
Potential Hazards to Humans, Environment, and Cultural Resources
Human safety. Moderate to High risk.This equipment employs high-power spinning cutting blades and therefore should be handled with extreme care. Users should receive training prior to operating equipment and utilize all recommended Personal Protective Equipment (PPE) that include ear, eye, face protection as well as gloves. Follow all safety instructions in the manual or your agency guidelines. Prolonged use can also cause repetitive stress injury from vibrating handles. Prolonged exposure to exhaust fumes can increase a user’s risk of cancer. Hearing loss without proper ear protection may be a consideration.
Cultural resources. Moderate risk. Heavy equipment could impact subsurface resources. Grinding, if not aimed specifically on tree stumps could impact surface-scatter or buried resources immediately adjacent to target plants.
Sensitive Species.Low to Moderate risk.Wildlife may be nesting in the trees being removed. Nesting bird surveys should be conducted before cutting during breeding season (generally Feb. 1- Aug. 31) to minimize damage to nests. Wherever possible, use this technique outside of the breeding season. Negative impacts to non-target plant species pose a low-moderate risk. Identify sensitive plants in an area in advance and avoid impacting them.
Habitat.Moderate risk. Habitat alteration with this technique is high, but generally restricted to a small area.
Erosion. Moderate-High risk. Risk of erosion can be moderately high depending on equipment and site (steep slopes, low remaining vegetative cover) but is generally restricted to a small area.
Fire. Moderate to High risk. Equipment can create sparks which can cause fire. Minimize risk of fire by only using equipment during periods of low fire risk, removing rocks and other hard objects that could spark when hit by the blade, and having personnel with fire suppression equipment on site in case of ignition.
Consider Combining with the Following Non-Chemical Methods
Stumps must be cut by either chainsaw or hand saw prior to grinding. Also consider pairing grinding with manual whole plant removal in order to remove other life stages of the target plant.
Don’t Use This Technique When/For
Wet soil conditions will increase compaction and physical disturbance to a site by large machinery. Very dry, high fire risk conditions will increase the risk of fire. Rocky sites should be avoided.
References
https://www.homeadvisor.com/cost/landscape/stump-grinding
Picchio R, S. Verani, G. Sperandio, R. Spina, E. Marchi. 2012. Stump grinding on a poplar plantation: Working time, productivity, and economic and energetic inputs. Ecological Engineering 40: 117-120.
Truini, J. 2015. https://www.popularmechanics.com/home/lawn-garden/how-to/a129/stump-grinder-tips/
Authors and Credit
Lead Author:Pamela Beitz, Integrated Pest Management Specialist, East Bay Regional Parks District
Co-authors:
Andrea Williams, Marin Municipal Water District (former)
Additional Contributors: None
Efficacies
| Rating | |||
|---|---|---|---|
| Plant | Flowering Period | ||
| Winter | No Information | ||
| Spring | No Information | ||
| Summer | No Information | ||
| Fall | No Information | ||
| Multiple Seasons | No Information | ||
| None | No Information | ||
| Plant | Germination | ||
| Winter | Good | ||
| Winter / Spring | Good | ||
| Spring / Summer | Good | ||
| Opportunistic | Fair | ||
| Plant | Palatability | ||
| Yes | No Information | ||
| No | No Information | ||
| Partial | No Information | ||
| Plant | Plant Growth Form | ||
| Grass | N/A | ||
| Forb | N/A | ||
| Shrub | Good | ||
| Tree | Good | ||
| Vine | N/A | ||
| Plant | Plant Type | ||
| Annual | N/A | ||
| Biennial | N/A | ||
| Perennial | Good | ||
| Plant | Propagule Production | ||
| Low (<1000/square meter) | Good | ||
| Moderate (1000–10,000/square meter) | Good | ||
| High (>10,000/square meter) | Good | ||
| Plant | Rate of Spread | ||
| High (doubling in <10 year) | Good | ||
| Moderate (50–75% increase in 10 years) | Good | ||
| Slow Rate (25% increase in 10 years) | Good | ||
| Plant | Resprouting / Regenerative Capacity | ||
| Low | Good | ||
| Moderate | Good | ||
| High | Good | ||
| None | N/A | ||
| Plant | Seed Life | ||
| Short (≤3 years) | Good | ||
| Moderate (4–10 years) | Fair | ||
| Long (>10 years) | Poor | ||
| Plant | Type of Reproduction | ||
| Seed | Good | ||
| Vegetative | Good | ||
| Seed & Vegetative | Good | ||
| Plant | Type of Vegetative Reproduction | ||
| Rhizome / Stolon / Stem | No Information | ||
| Bulb / Corm / Tuber | N/A | ||
| Root sprout / Sucker / Crown sprout | Good | ||
| Site | Existing Desirable Plant Cover | ||
| <10% | Good | ||
| 10–25% | Good | ||
| 26–50% | Fair | ||
| 51–75% | Poor | ||
| >75% | Poor | ||
| Site | Ground Condition | ||
| Muddy | N/A | ||
| Smooth | Good | ||
| Cobbly | Good | ||
| Rocky | Good | ||
| Site | Habitat | ||
| Marsh / Wetland | N/A | ||
| Riparian | N/A | ||
| Grassland | Good | ||
| Shrubland | Good | ||
| Woodland / Forest | Good | ||
| Site | Level of Tolerable Disturbance | ||
| Low | Ineffective | ||
| Medium | Fair | ||
| High | Good | ||
| Site | Slope | ||
| Flat | Good | ||
| Moderate (10–40%) | Fair | ||
| Steep (>40%) | N/A | ||
| Site | Target Area | ||
| <40 square feet | Good | ||
| 0.001–0.01 acre | Good | ||
| 0.02–0.1 acre | Good | ||
| 0.2–1 acre | Good | ||
| 2–10 acres | Fair | ||
| 11–50 acres | Poor | ||
| 51–100 acres | Poor | ||
| >100 acres | Ineffective | ||
| Site | Targeted Invasive Plant Cover | ||
| <1% | Good | ||
| 1–10% | Good | ||
| 11–25% | Good | ||
| 26–50% | Fair | ||
| 51–75% | Poor | ||
| >75% | Poor | ||
| Site | Vehicle Accessibility | ||
| Roadside | Good | ||
| <100 feet from road | Good | ||
| 100–1000 feet from road | Fair | ||
| >1000 feet from road | N/A | ||
