Introduction to Physical Removal of Woody Invasive Species
Physical removal of woody invasive plants consists of removing entire plants, root systems and all, from the places where they are growing. Approach can range from very low-tech in the case of hand-pulling, to operation of heavy equipment. Woody invasive plants can develop extensive root systems that are difficult to remove once plants are well-established. This makes hand pulling practical for relatively small to moderate sized plants. Use of heavy equipment for removal may be suitable for sites with dense, mature invasive populations, but often carries significant equipment and labor costs. Any removal effort causes soil disturbance which can promote germination of invasive plant seeds and damage the roots of desirable plants in the area (Miller et al. 2015).
How it works
Plants are physically removed from the soil, including as much of the root system as possible.
Methodology in Detail
Once woody invasive plant seedlings are correctly identified, they can be pulled by grasping the stems near the base and tugging sharply with gloved hands. A simple garden tool such as a trowel, hand rake or dandelion digger may be used to loosen soil around the roots, if necessary. This will be most easily accomplished in moist uncompacted soil. Soil disturbed by hand-pulling can be tamped down with boots to reduce invasive seed germination (Miller et al. 2015).
Invasive woody plants often develop robust root systems by the time they are 3-5 years old making hand pulling more difficult. Specialized leverage tools –both hand tools and vehicle attachments– can assist in uprooting larger plants. Hand tools vary by model, but generally work by gripping the stem near the soil surface and prying the root crown out of the ground. There is a usually a foot plate, which stabilizes the tool, a fulcrum near the point of attachment, and a long handle which is pushed downwards to produce upward force used to pull the target out of the ground. These tools are usually rated according to the ratio by which they multiply the force exerted on the handle. For example, a tool with an 8:1 ratio will exert 80lbs of upward force on the target stem for every 10lbs of downward pressure applied to the handle (Miller et al. 2015). Brand names of these tools include Extractigator®, Honeysuckle Popper®/Shrub Buster®, Root Talon, Uprooter, and WHaTS post and shrub puller. Non-specialized hand tools such as shovels, mattocks, and pulaskis may also be used to remove or loosen soil and to grub out shallow roots.
Vehicle-mounted tools are generally either chain-type attachments that are wrapped around target stems or grabbing attachments with toothed jaws that are clamped to stems. A vehicle with a tow hitch such as an ATV, UTV or a vehicle with a hydraulic system such as a tractor or skid steer provides the force for uprooting. Attachment tools are made in a variety of sizes. Instructions and safety precautions provided by vehicle and attachment manufacturers should always be followed carefully as they can be very dangerous if misused. Similar to hand-pulling, equipment-assisted pulling is easiest in moist soil and may not be practicable in rocky or dry soils or on steep slopes.
The roots of large trees or shrubs can be physically removed by cutting the target down and then using a stump grinder to remove the stump and root crown. This a very labor intensive and expensive process rarely used in natural resource management. Dense infestations can be excavated with heavy equipment like forestry dozers, skid-steer loaders or tractors with various digging, raking and grubbing attachments. This approach is generally only used for natural areas management if there are no desirable species left in the understory. Use of heavy equipment causes a lot of soil disturbance, which promotes a resurgence of invasive species from seed (Miller et al. 2015).
Some woody invasive species produce root suckers, which are shoots that grow from the root system of an established tree or shrub but look very similar to seed-generated plants from above ground. Root suckers are connected to a large, mature root system so pulling them is not feasible, and damage to suckers can promote additional root sprouting (Fryer 2011). Invasive woody species known for aggressive root sprouting include black locust, white poplar, tree-of-heaven, Russian and autumn olives, and Oriental bittersweet.
Hand and equipment assisted pulling of seedlings and small plants can be done any time of year when the soil is not frozen, though removal prior to fruit production is ideal. It is easiest to pull plants during the spring and fall, when soils tend to be moist and temperatures are relatively cool.
Removal of large infestations with heavy equipment is best conducted in winter when soil is frozen to minimize soil disturbance (Butler Soil and Water Conservation District).
Roots of pulled or excavated plants should not be left in contact with soil as re-rooting is possible. See disposal guide for options.
If invasive plant seeds are likely present on site (e.g., the plants being pulled are fruiting or have fruited previously), all equipment and operator clothing and footwear should be cleaned before leaving the site to prevent spreading invasive plant seeds to new locations.
Any invasive species treatment needs to be monitored for effectiveness and for invasive species re-growth in the years following treatment. Soil disturbance caused by uprooting plants may cause the target species or different invasive species to emerge from the seedbank. Incomplete removal of the root system is likely to result in regrowth of many woody invasive species.
Butler Soil and Water Conservation District. Amur honeysuckle identification and removal. https://www.butlerswcd.org/honeysuckle-remediation
Miller, JH, Manning, ST and SF Enloe. 2015 (rev). A Management Guide for Invasive Plants in Southern Forests. United States Department of Agriculture, Forest Service, Southern Research Service. SRS-131.
Photo Credit: Clair Ryan, Midwest Invasive Plant Network