Girdling is a technique that kills woody plants in place without cutting them down. It uses a sharp tool to cut through the bark of a woody plant in a strip all the way around the stem down to the wood. This severs the vascular cambium of the woody plant and cuts nutrient flow between the foliage and the roots. As a result, roots are starved of nutrients and the plant cannot grow more stems and foliage. Unless the plant can heal over the wound it will die unless it has reproductive capacity to send up resprouts.
Girdling is often used to control or eradicate large woody species where physical removal of woody biomass would be undesirable, unpopular, or cost prohibitive. Killing an undesirable tree in place by girdling also has the benefit of leaving standing snags for wildlife. Additionally, there is lower visual impact where the sudden removal of an entire stand would affect the areas aesthetics. Since die-off is gradual (taking months to years), the visual change in the area is slower. Killing mature trees slowly can also give replacement plantings time to grow, so more mature habitat is in place once treatment is complete. With some species the shade produced by the dying trees can reduce the amount of suckering or other regeneration of the target species compared to techniques that remove biomass, thus opening the canopy and stimulating sucker growth.
Girdling is a useful technique to remove trees in areas within public view, when raptors are using trees, at remote sites where other techniques are impractical, or when maintaining a density of trees or large shrubs is necessary. This technique generally has a low impact on cultural resources, erosion and surrounding habitat because it is highly selective and does not disturb soil. It is well-suited for remote sites because all tools needed for girdling can be carried by hand; it is also labor intensive and therefore inefficient for large stands of trees. When used alone girdling is an effective control method for some species of mature woody plants, but not for very young plants. When combined with other techniques targeting seedlings and younger saplings, it can be part of a strategy to eradicate woody invaders.
How to Use
When used as a non-chemical control technique, girdling works by severing nutrient flow from above-ground portions of a woody plant to its roots and water flow from roots to leaves. It is only effective if the inner bark is completely severed around the circumference of a trunk and not allowed to regrow. A sharp tool is used to sever the outer and inner bark (cambium) around the entirety of all stems in either a ring (bark-ringing) or a series of overlapping cuts (frilling). This may be repeated in multiple sections, or the bark may be stripped to the ground (bark peeling). Girdling is most effective when done just after a tree leafs out for the growing season, when it has used a maximum amount of its stored carbohydrates for new growth and well before it has begun to transition back into dormancy.
There are various ways of implementing this technique. One method is to use a chainsaw to cut three rings fully around the target trunk through the bark and cambium layer. Cuts should each be a few inches wide and a few inches apart. Another method is to cut and strip the bark in a 6-8” solid band around the trunk. This may require a chainsaw, hatchet, machete, etc. to cut through the bark at the edges of the peel area. Land managers frequently use these two girdling methods for Douglas fir and cultivars of Monterey pine growing in areas where they are not desired. Frilling is done by cutting overlapping slashes into the trunk at a downward/inward angle, cutting through into the wood and leaving a “frilly” appearance hence the name.
The tools used for these techniques vary by target species and user comfort. For species with thin bark and younger growth, a sharp, strong hand tool such as a machete (used with caution) or hatchet (generally safer) can be used. Chainsaws are often the tool of choice for more mature trees with thick bark. All tools will need to cut through the bark layer and cambium down to the underlying wood. It is important to be familiar with the thickness of the bark and cambial layer in the species being treated prior to choosing a tool. Multiple tools may be effective, so tool choice may be dictated by safety and ease of use. Low branches may need to be trimmed to be able to access the main trunk of a tree or shrub for girdling. If a tree or shrub is multi-trunked, all main stems will need to be girdled.
As each tree is treated individually this technique is highly selective. Non-target damage is only expected if the non-target species is growing close enough to the target that it impedes maneuverability around the target trees/shrubs with the cutting tools. In this case non-target damage may include broken branches and vines.
Girdling can be effective any time of year but is expected to be more effective when the target species is preparing to go into dormancy at the end of the growing season (leaves still green). Because girdling prevents nutrients from traveling down into the roots, it is most effective after the plant has utilized carbohydrate reserves in roots for growth in the spring and before it sends reserves back down to roots in the fall. If done too early (new leaves still flushing or at the beginning of a long growing season), the plant may be able to heal in time to replenish carbohydrates. If done nearing leaf drop, the plants may already have enough nutrient stores to survive dormancy, heal, and regrow.
Cutting multiple bands of bark rings or frills or making the bands thicker (from a few to 12+ inches), can help to prevent regrowth of bark when dealing with trees with lots of knots in the trunk.
Revisiting the treatment site is recommended to ensure that the cambium has not regrown across the cuts, especially with Eucalyptus and other resprouting woody species. Resprouts will need to be cut repeatedly to fully exhaust energy stored in the roots.
Some practitioners have experimented with covering and sealing girdle cuts with black plastic to prevent resprouts. This technique may be useful in remote areas where treated trees cannot be checked frequently, though tarping also requires regular maintenance. Some species, like tree-of-heaven, can send up sprouts from roots some distance from the main stem.
Optimal Conditions for Use
Girdling is most effective on species that do not resprout, in drier site conditions, and when applied before plants begin to store nutrients for dormancy. It is most effective on mature trees, older brooms and other mature shrub species. Non-resprouting conifers, and some tree species that resprout from lignotubers rather than lateral roots are especially susceptible to girdling. Trees in open landscapes, such as grasslands, are easier to access for girdling and to track after treatment.
This technique should only be used where standing dead trees and the associated risks—for instance, fallig branches–can be tolerated. It should also not be used in areas where eradication is the immediate management objective because a girdled tree can take months to years to die, during which time it can still produce viable seeds and other reproductive structures.
When cutting, pay special attention to any undulations in the trunk shape as the cambium will undulate as well and may be difficult to sever completely.
Girdling may be less effective under wet conditions where plants have a greater chance of resprouting. It is also less effective for younger, vigorous trees and shrubs that can more easily regrow.
Girdling (without supplemental herbicide treatment) is generally not recommended for eucalyptus, tree-of-heaven and other woody species which can resprout prolifically.
Potential Hazards to Humans, Environment, and Cultural Resources
Human safety: Moderate. Hazards include cutting risk by workers using sharp hand tools and chainsaws. Hazards of these tools differ based on many factors including familiarity with the tool used, target species, field conditions, etc. Generally, chainsaws are more hazardous than machetes, which are more hazardous than hatchets. Maintain a suitable safe distance between workers, and ensure they have any PPE associated with the chosen work tools Ensure workers are trained to use these tools safely in relation to the individual environmental hazards of the work site. Be aware of and address tree deadfall risks after girdling.
Cultural resources: Low. Girdling does not impact surface and subsurface cultural resources.
Habitat: Low. There is little concern of hazards to nontarget species or the environment because of the high specificity of this technique. Over time, the treated vegetation may pose a falling hazard after they die. The technique therefore holds a delayed potential for environmental hazards and long-term loss of nesting habitat. This technique can also increase fuel loads, especially in the canopy. Treatments should be timed and spaced to prevent accumulation of fuels in case of a wildfire. This is likely a short-term risk as fine fuels will fall off the tree relatively quickly after tree death. These hazards can both be reduced by removing the biomass of dead individuals after treatment takes effect. Removal of this kind often comes with a high cost.
Sensitive species: Low. Be aware and mitigate as needed for changes in raptor perch and nesting opportunities long-term.
Erosion: Low. There is no ground disturbance. In the long-term, other vegetation will need to establish to hold soil in place.
Consider Combining with the Following Non-Chemical Methods
Girdling may be an effective addition to tarping a cut stump of a resprouting species. For this, the cut stump should be girdled below ground level before tarping to reduce resprouting. Bark peeling can also reduce regrowth of cut stumps. Use of this combination of techniques requires extensive effort, first to fell the tree, thn to dig an adequately sized hole, and finally to implement the girdle band below the soil surface.
Girdling may be combined with competitive planting of desirable species. Smaller invasive plants can be removed using a variety of other tools and approaches.
Don’t Use This Technique When/For
This technique is ineffective on seedlings and saplings, palm trees, species with undulating bark, and species with the ability to resprout from roots. For resprouting species, such as eucalyptus, black locust (Robinia pseudoacacia), or tree-of-heaven (Ailanthus altissima) girdling may actually increase the cover of a problem tree by triggering heavy resprouting. Do not use this technique on Girdling is difficult on multi-trunked trees and shrubs like castor bean (Ricinus communis).
Annighöfer, P., P. Schall, H. Kawaletz, I. Mölder, A. Terwei, S. Zerbe, and C. Ammer. 2012. Vegetative growth response of black cherry (Prunus serotina) to different mechanical control methods in a biosphere reserve. Canadian Journal of Forest Research 42: 2037–51.
Kilroy, B and KWindell. 1999. Tree Girdling Tools. USDA Forest Service Publication 9924-2809. Missoula, MT.
Merceron, N., L. Lamarque, S. Delzon, A. Porté. 2016. Killing it Softly: Girdling as an Efficient Eco-Friendly Method to Locally Remove Invasive Acer negundo. Ecological Restoration 34: 297 – 305.
Muvengwi, J., M. Mbiba, L. Jimu, A. Mureva, B. Dodzo. 2018. An assessment of the effectiveness of cut and ring barking as a method for control of invasive Acacia mearnsii in Nyanga National Park, Zimbabwe. Forest Ecology and Management 427: 1-6.
Authors and Credit
Lead Author: Shani Pynn, Senior Plant Restoration Ecologist, Riverside Corona Resource Conservation District
Pamela Beitz, Integrated Pest Management Specialist, East Bay Regional Parks District
Ken Moore, Wildlands
Tom Reyes, Integrated Pest Management Coordinator, Midpeninsula Regional Open Space District
|Winter / Spring||No Information|
|Spring / Summer||No Information|
|Plant||Plant Growth Form|
|Low (<1000/square meter)||Good|
|Moderate (1000–10,000/square meter)||Fair|
|High (>10,000/square meter)||Ineffective|
|Plant||Rate of Spread|
|High (doubling in <10 year)||Poor|
|Moderate (50–75% increase in 10 years)||Poor|
|Slow Rate (25% increase in 10 years)||Good|
|Plant||Resprouting / Regenerative Capacity|
|Short (≤3 years)||Good|
|Moderate (4–10 years)||Fair|
|Long (>10 years)||Poor|
|Plant||Type of Reproduction|
|Seed & Vegetative||Poor|
|Plant||Type of Vegetative Reproduction|
|Rhizome / Stolon / Stem||Ineffective|
|Bulb / Corm / Tuber||Ineffective|
|Root sprout / Sucker / Crown sprout||Fair|
|Site||Existing Desirable Plant Cover|
|Marsh / Wetland||Poor|
|Woodland / Forest||Good|
|Site||Level of Tolerable Disturbance|
|<40 square feet||Good|
|Site||Targeted Invasive Plant Cover|
|<100 feet from road||Good|
|100–1000 feet from road||Good|
|>1000 feet from road||Good|