Trees, perennial grasses, shrubs
Indiscriminate
Moderate–high ($1000–$5000/gross)
Low/no risk
Low risk
Low risk
Moderate (erosion, sensitive plants, ground-dwelling animals)
Overview
Tarping involves using heavy plastic, polypropylene, or other light-blocking material to cover the ground in order to prevent weed growth. Tarps can also be used to cover tree stumps to prevent resprouting. Tarps are usually durable enough that they can be stored and reused multiple times. Because tarps must be left in place for several months in order to be effective, this method is most practical for small areas and to stop an isolated infestation or to contain a part of a localized weed patch to prevent expansion while the rest is treated.
Tarps placed on the ground will suppress plant growth by both blocking light, which is required for growth, and by stimulating (some) seed germination, by maintaining moist conditions. When the seeds emerge from the soil, they quickly die due to the lack of light thereby reducing the population in the soil seed bank. Surface tarps are left in place for weeks to months to even years, depending on the species being treated and its ability to regrow.
Tarps can also be used to reduce the effect of resprouting from cut stumps by blocking light to the newly sprouted buds or controlling sprouting from rhizomes, stolons, bulbs, and other vegetative propagules. Tarps used for this purpose cover a much smaller area such as only the stump or small planting bed and are also left in place for months to years.
How to Use
Tarping is most effective if the target area is exposed to full sunlight. For best results, use 6 mil UV-protected black plastic or black or brown plastic tarps with grommets.
For seed bank reduction: Mow the area as low as possible to provide an even surface to lay the tarp. Where permissible, till the site to be able to lay the tarp flat. Cover site with tarp and hold in place with sandbags, rocks, filled erosion socks, duck-billed anchors, U-nails, or other fasteners. Leave on for 3 to 6 months during the period of germination for the plants of concern. Remove tarp and plant desirable species into the area, minimizing soil disturbance so as not to move any weed seeds to the surface.
For treating perennial plants: Cut or mow plants to a height of less than 6 to 8 inches. Cover area with tarp and hold in place with sandbags, rocks, filled erosion socks, duck-billed anchors, U-nails, or other fasteners. Tarps must extend well beyond the perimeter of the patch being treated, farther than where plants will send out lateral shoots (ideally greater than 6 feet). Monitor for runners that may emerge along edges. Depending on species, the tarp may be removed in 6 months for many herbaceous species to 2 or more years for plants with resprouting roots or deeper rhizomes or seasonal resprouting. Monitor and hand remove any new sprouts. See Supplementary Information for specific instructions on tarping Arundo and pampasgrass.
For treating stumps: Cut stump low and level to the ground and clear a space around the stump to be tarped. It may be helpful to dig a trench around the stump to facilitate tarp placement. For trees that are prone to sprouting, 3 layers of 6 mil tarp can be used. See Supplementary Information for specific instructions on tarping Eucalyptus stumps and Acacia.
Spread tarp, anchor around edges with U-nails and/or duck-billed anchors. Some practitioners tie the tarp on tree stump. Avoid holes in tarp. Extend the tarp far enough beyond target so that sprouts, runners, etc. will not emerge past the tarp. If possible, cover with chips or other plant material. Check regularly to ensure that the tarp is still in place and intact. Allow the tarp remain in place for several years.
Special Tips
On rocky slopes, wet areas, uneven ground, or ground with large amounts of duff, use longer staples or anchors (at least 12 inches).
Commercial plastic tarps are expensive but do not degrade. Permeable weed cloth, in contrast, will deteriorate too quickly, even if installed in two layers.
Tarps must be patched if damaged or else light will get through and the weeds will continue to grow. While duct tape can be used, tape that is specific for tarps will provide a longer-term repair, is UV resistant, waterproof and bonds better than duct tape.
Optimal Conditions for Use
Tarping works best on smooth, flat areas with highly isolated plants or patches generally less than 40 ft2. This can also be effective on large areas with many isolated patches. It also works best on tree stumps if they are cut low and level to (ideally below) the ground.
Caveats
- This technique is non-selective. It will kill all plants it covers.
- It takes time—often takes a year or more of tarping—to see good results.
- Tarps must be checked regularly for holes and to make sure they are secured.
- Tarping in public areas may result in tarps being damaged or stolen.
- Tarps draw attention and may be perceived as trash that should be removed. Add signage to limit curiosity.
- Long-term tarping, for example 1 year or more, has unknown effects on local soil biota.
Potential Hazards to Humans, Environment, and Cultural Resources
Human safety. Low risk. Best practices should be used when using tools to install tarps to avoid injury. Tripping could be a problem so it is not recommended to use over trails or in areas of high foot traffic.
Cultural resources. Low risk. Digging around stumps to secure tarps could impact buried resources if they are directly on site.
Habitat. Low risk. This technique is typically used for small contiguous patches of single species or stumps. Tarping should be removed from site after use.
Sensitive species. Low risk. Immobile species, for example plants and some soil dwellers, may be impacted. Species trapped under plastic, for example snails or lizards, will be impacted. Do not use tarps over sensitive plants or in areas where sensitive animals have been documented. Tarps will kill almost everything under them.
Erosion. Low risk. Tarps will protect sites and will minimize soil disturbance. However, if a tarp is on a slope, the unprotected areas down slope from the tarped area will be susceptible to erosion. Bare areas exposed after tarping will be vulnerable to erosion.
Consider Combining with the Following Non-Chemical Methods
Tarping applied in combination with a mow-and-till treatment was effective at controlling perennial pepperweed. Mow–Till–Tarp treatment is extremely time consuming and has the potential to limit native plant community recovery.
Don’t Use This Technique When/For
Avoid tarping large (>0.01 ac) areas and areas where the tarps may be disturbed. This technique is probably not a first choice for prolonged, continuous coverage of large areas, due to the associated destruction of habitat and soil organisms.
Supplementary Information
The following materials have been used successfully by practitioners for specific weed issues:
- Thick tarp (e.g., Merafi 800) is good for perennial woody species with complex root structure if herbicide is not an option. It has been used effectively on Spartina as well.
- Biotelo is a tarp material that allows no light penetration and is biodegradable. It has worked on pampasgrass and Arundo and was installed after winter rains. Plants were killed after 6 months.
- A standard brown tarp with grommet holes, covered with duff, has worked in public areas for pepperweed and Calystegia sepium.
Below are tarping tips for specific weed species:
Acacia
- Dig trench around plot 2 ft from nearest stump and 1 ft below grade.
- Cut to within 12 inches of grade (lower is better).
- Tarp stumps with 3 layers of 6 mm black plastic.
- Backfill trench.
Notes: Tarps can be covered with duff. Tarps may not hold on steep hillsides.
Pampasgrass (Cortederia sp.)
- Cut off stalks and leaves as low and flat to the ground as possible.
- Cut off seed part of stalks and dispose of safely.
- Cover plants with biodegradable tarps.
- Secure the tarp over the clump with staples, washer pins, or rocks or other heavy objects from the site. Staples are more appropriate for non-rocky soils and should be pounded in with a dead blow hammer about every 2 feet around the perimeter or closer if needed. More rocky ground may require washer pins and a 3-lb sledgehammer, applied at the same spacing.
- Pile all of the stalks and leaves on top of the plants to keep tarps in place and to obscure from view by passersby.
Arundo
From: Center for Ecological Restoration And Stewardship Circuit Rider Productions, Inc. (2007).
- Cut the stalks to a standard height as close to the ground as possible. Make sure that the cuts are level, not angled. Stalks cut at an angle could cause serious injury if a fall occurs, and may poke holes in the tarp. If the site can be cleaned up to make the tarp installation easier, do so—remove brush, litter, or any object that may interfere with the tarp laying flat.
- Measure the longest width by the longest length of the clump and add about 10% or 4 feet, whichever is smaller.
- Cut the tarp to this measurement. Use tarp pieces as large as possible to minimize any “quilting effect”—the Arundo growing between tarp edges. The tarping material often comes in 12-ft rolls, so for larger clumps some overlapping of pieces may be necessary. Keep in mind that larger tarps are easier to reuse because they can be cut smaller if necessary.
- Secure the tarp over the clump footprint with staples, washer pins, or rocks or other heavy objects from the site. Staples are more appropriate for non-rocky soils and should be pounded in with a dead blow hammer about every 2 feet around the perimeter, or closer if needed. More rocky ground may require washer pins and a 3-lb sledgehammer, applied at the same spacing. Sometimes rocks or deadwood can be used to secure the tarp, but don’t mine the surroundings. Use these materials only if the other methods are not working and use them sparingly.
- Monitor the tarp every two weeks, patching any holes that occur. Avoid walking over the tarps as much as possible. Even a very small hole can provide enough light for the Arundo to survive.
- Timing is crucial to the effectiveness of tarping. Tarps should be laid during the active growing season and when there is minimal risk of being dislodged by floodwaters. In the Russian River watershed, the time period stipulated is May 1 through October 31, unless installed safely outside of the flood area. Tarps must remain in place at least six months to be effective, and often need to be reapplied the following season to allow for complete kill. The area should be monitored for at least an additional growing season after the tarp has been removed to ensure the root mass will not resprout.
Materials for tarping Arundo:
- Tarping material. Choose a plastic material that is completely impermeable to light, as even a small amount of light can allow the root mass to survive. Hold a sample up to a bright light to verify. The material should also be of sufficient strength to keep resprouting stalks from poking through. A tensile strength of 200 lbs has proven sufficient. Finally, the material should be sufficiently pliable and lightweight as to be easy to use (usually a thickness of 12 mil).
- Tape measure
- Cutting implement
- Staples (12 inches, 9 gauge) staples for non-rocky ground
- Washer pins (12 inches, 7 gauge) for cobble or other rocky areas. These are headless nails with a bulge at the top and a washer attached below the bulge.
- Dead blow hammer (with staples) or 3-lb sledgehammer (with washer pins)
- Proper protective clothing: long pants and long sleeves, eye protection, gloves, and boots.
Eucalyptus stumps
- For large diameter eucalyptus trees: to be cut 4 to 6 inches from the ground with the cuts angled to match the land’s contours.
- For small diameter eucalyptus trees (up to 6 inches in diameter): to be cut as close to the ground as possible for either tarping or removal with a weed wrench.
- Clear duff away from around the stump and create a small trench around it.
- Cut the tarping material, adding about 10% to the longest width by the longest length of the stump or clump of stumps (if covering more than 1 stump at a time).
- Secure the tarp over the stump or around the clump footprint with staples, washer pins, or rocks or other heavy objects from the site. Staples are more appropriate for non-rocky soils, and should be pounded in with a dead blow hammer about every 2 feet around the perimeter, or closer if needed. More rocky ground may require washer pins and a 3-lb sledgehammer, applied at the same spacing. Rocks or deadwood can be used to secure the tarp, but use these materials only if the other methods are not working, and use them sparingly.
- Cover the stump or clump with chips or other onsite organic debris.
- Avoid walking over the tarps and monitor them regularly. Tarps must remain in place at least six months to be effective, and may need to be reapplied the following season to allow for complete kill. The area should be monitored for at least an additional growing season after the tarp has been removed to ensure the root mass is not resprouting.
Materials for tarping eucalyptus:
- Tarping material: black plastic.
- Tape measure; cutting implement; staples (12 inches, 9 gauge) staples for non-rocky ground; washer pins (12 inches, 7 gauge) for cobble or other rocky areas; dead blow hammer (with staples) or 3-lb sledgehammer (with washer pins)
- Proper protective clothing: long pants and long sleeves, eye protection, gloves, and boots
References
California Invasive Plant Council. 2004. A Guide to Techniques for Removing Bay Area Invasive Plants. https://www.cal-ipc.org/docs/ip/management/wwh/pdf/18601.pdf. Pp. 38, 93.
Hutchinson R.A. and J.H. Viers. 2011. Tarping as an alternative for perennial pepperweed (Lepidium latifolium) control. Inv. Plant Sci Manage. Invasive Plant Science and Management. 4:66–72.
Maher, R. 2018. Take Me Out to a Tarped Field. Cornell Small Farms Program. https://smallfarms.cornell.edu/2018/04/take-me-out-to-a-tarped-field-needs-sidebar/
Matzek, V. and C. Sifuentes-Winter. 2020. Non-herbicidal measures of control for slender false brome (Brachypodium sylvaticum), an invasive perennial grass. Cal-IPC Symposium presentation, online. https://www.cal-ipc.org/resources/symposium//nonherbicidal-measures-of-control-for-slender-false-brome-brachypodium-sylvaticum-an-invasive-perennial-grass/cal_ipc_symposium_2020_virginia_matzek_non-herbicidal-control-measures-for-slender-false-brome-brachypodium-sylvaticum/
Authors and Credit
Lead Author: Cheryl Wilen, Integrated Pest Management Specialist, University of California
Co-authors:
Margot
Cunningham, Natural Areas Coordinator, City of Albany
Sandy
DiSimone,
Science Director, Audubon Starr Ranch
Susan
Schwartz, President,
Friends of Five Creeks
Additional Contributors:
Pete Frye,
Independent
Contractor
Matt
Horowitz, Program
Director, Natural Resources and Employment Program
Jane Kelly, Co-founder, KyotoUSA
TomKelly, Executive Director, KyotoUSA
Suggested Citation:
Wilen, C., M. Cunningham, S. DiSimone and S. Schwartz. Tarping. Weed Control User Tool (WeedCUT) – Methods for Managing Weeds in Wildlands. weedcut.ipm.ucanr.edu. California Invasive Plant Council (Cal-IPC) and University of California Statewide Integrated Pest Management Program (UC IPM). Accessed [date].
Efficacies
| Rating | |||
|---|---|---|---|
| Plant | Flowering Period | ||
| Winter | Good | ||
| Spring | Good | ||
| Summer | Good | ||
| Fall | Good | ||
| Multiple Seasons | Good | ||
| None | Good | ||
| Plant | Germination | ||
| Winter | Good | ||
| Winter / Spring | Good | ||
| Spring / Summer | Good | ||
| Opportunistic | Good | ||
| Plant | Palatability | ||
| Yes | No Information | ||
| No | No Information | ||
| Partial | No Information | ||
| Plant | Plant Growth Form | ||
| Grass | Excellent | ||
| Forb | Excellent | ||
| Shrub | Good | ||
| Tree | Excellent | ||
| Vine | Fair | ||
| Plant | Plant Type | ||
| Annual | Excellent | ||
| Biennial | Excellent | ||
| Perennial | Excellent | ||
| 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) | Excellent | ||
| Plant | Resprouting / Regenerative Capacity | ||
| Low | Excellent | ||
| Moderate | Good | ||
| High | Good | ||
| None | Excellent | ||
| Plant | Seed Life | ||
| Short (≤3 years) | Excellent | ||
| Moderate (4–10 years) | Fair | ||
| Long (>10 years) | Fair | ||
| Plant | Type of Reproduction | ||
| Seed | Good | ||
| Vegetative | Good | ||
| Seed & Vegetative | Good | ||
| Plant | Type of Vegetative Reproduction | ||
| Rhizome / Stolon / Stem | Good | ||
| Bulb / Corm / Tuber | Fair | ||
| Root sprout / Sucker / Crown sprout | Good | ||
| Site | Existing Desirable Plant Cover | ||
| <10% | Excellent | ||
| 10–25% | Poor | ||
| 26–50% | Ineffective | ||
| 51–75% | Ineffective | ||
| >75% | Ineffective | ||
| Site | Ground Condition | ||
| Muddy | Good | ||
| Smooth | Excellent | ||
| Cobbly | Fair | ||
| Rocky | Fair | ||
| Site | Habitat | ||
| Marsh / Wetland | Fair | ||
| Riparian | Good | ||
| Grassland | Good | ||
| Shrubland | Good | ||
| Woodland / Forest | Good | ||
| Site | Level of Tolerable Disturbance | ||
| Low | Poor | ||
| Medium | Fair | ||
| High | Excellent | ||
| Site | Slope | ||
| Flat | Excellent | ||
| Moderate (10–40%) | Good | ||
| Steep (>40%) | Good | ||
| Site | Target Area | ||
| <40 square feet | Excellent | ||
| 0.001–0.01 acre | Good | ||
| 0.02–0.1 acre | Good | ||
| 0.2–1 acre | Ineffective | ||
| 2–10 acres | Ineffective | ||
| 11–50 acres | Ineffective | ||
| 51–100 acres | Ineffective | ||
| >100 acres | Ineffective | ||
| Site | Targeted Invasive Plant Cover | ||
| <1% | Excellent | ||
| 1–10% | Good | ||
| 11–25% | Good | ||
| 26–50% | Good | ||
| 51–75% | Good | ||
| >75% | Good | ||
| Site | Vehicle Accessibility | ||
| Roadside | Good | ||
| <100 feet from road | Good | ||
| 100–1000 feet from road | Good | ||
| >1000 feet from road | Good | ||
