Public Works and Environmental Services Alert:
Management of invasive plants can appear to be a complicated and unending task. A variety of methods are used to control invasive plants. How effective the control method is varies with the skill of application, the type of infestation, and many other factors. The majority of these methods described are most effective when used in combination. For recommendations specific to your property, consult a professional invasive species management company. It is important to wear gloves, long pants and long sleeves to avoid skin contact with many plants and check yourself for ticks.
It is important to learn about the life cycle of each plant you are trying to control so that you effectively time your efforts. The life cycle of a plant is simply its seasonal pattern of growth and reproduction.
Be conscious of erosion and soil disturbance caused by clearing land. If removing the plant from the root will cause damage to other plants or increase erosion, other options include cutting/girdling, or chemical control.
The removal of vegetation, such as groundcover, turf and plants, is considered land disturbance. Removal of vegetation in excess of 2,500 square feet is subject to Chapter 104 of the Fairfax County Code, the Erosion and Sediment Control Ordinance. For more information, visit Land Disturbance 101 – Before you Dig! Additionally, proper management of invasive plant species in a Resource Protection Area (RPA) requires prior approval from the Department of Land Development Services (LDS), regardless of the size in area. For more information, to include the proper request form, visit the LDS RPA webpage.
Certain cultural practices, like using native plants rather than invasive ones, can help slow the spread. You can directly aid with cultural control by learning which plants are invasive in your area and taking steps to manage them.
When possible, buy locally-grown plants to prevent introducing invasive seeds.
When maintaining your yard, properly dispose of the invasive debris in the trash.
When using a professional lawn care service, it’s good to find out their invasive species management practices, such as cleaning their equipment between client visits. This can help prevent the spread of invasive plants among neighborhoods.
Mechanical or manual controls are physical methods which are often the most straightforward way to control small areas of invasive plants. Physical methods entail any means of mechanically removing the plant, by cutting, smothering, pulling, or digging up the plants. In many cases, invasive plants readily re-sprout from fragments of roots that remain in the soil. It is important to thoroughly remove all parts of the plant, and to keep a close eye on the area in future years to remove any re-growth that may occur.
Cutting or girdling alone is usually counter-productive for invasive species, such as tree-of-heaven (Ailanthus altissima).The tree responds by producing large numbers of stump sprouts and root suckers. Learn more about Chemical Control.
For small infestations, repeated cutting of sprouts over time can exhaust the plants reserves and may be successful if continued for many years or where heavy shade exists.
If possible, the initial cutting should be in early summer in order to impact the tree when its root reserves are lowest. Cutting large seed producing female trees would at least temporarily reduce spread by this method.
An ISA certified arborist should be consulted for removal if a large tree is located near any structures, sidewalks, play areas or any location that a falling tree could damage. For more information contact the Urban Forester of the Day during regular business hours at 703-324-1770, TTY 711 or treemail@fairfaxcounty.gov.
Removing shrubs manually depends on the situation. Be sure to remove as much soil as possible from the roots with a weed wrench or other gardening tools. Be sure to remove as much soil as possible and tamp down the soil from the open hole and cover it with leaves. The point is less soil disturbance and more fruiting plant debris removal.
You can also cut the shrub near the ground and repeat as needed until it stops resprouting. Chemical control is also an option.
Manual control is the most targeted method, with the least likelihood of damage to other plants. However, it is slow and labor-intensive and best suited for fairly small, readily accessible infested areas.
Know the difference between native and invasive vines. Recognizing Invasive Species
For small infestations, plants can be hand-pulled, also called grubbing, removing all the roots. If fruits are present, the vines should be bagged in plastic trash bags and disposed of with the trash or, alternatively, piled up and allowed to dry on your property. Dried piles of pulled vines can either be left and monitored the next year for new growth or put out with your trash.
For vines climbing on trees, cut high and cut low to make a window. Bag if it has seeds. First cut the vines near the ground at a comfortable height to kill upper portions and relieve the host tree. Vines can be cut using pruning snips or a pruning saw for smaller stems and a hand axe or chain saw for larger stems. Try to minimize damage to the host tree’s bark. Pull the roots, repeatedly cut to the ground, or treat with herbicides. Cutting without herbicides will require vigilance and repeated cutting because new plants will resprout from the stem base.
Hand weeding is most effective early in the growing season (April-May) while the roots are small and before the vines become tangled with other vegetation. Monthly pulling and monitoring will be needed until the infestation is eradicated.
Visit Rescuing Trees, Plant NoVA Natives Tree Rescuers for more information.
The best time to pull groundcover is before the plant goes to seed and when the ground is soft. If all the roots are not removed, vigilance and repeated pulling will be required to eradicate the plant.
For larger infestations, or when hand-pulling is not practical, flowering stems can be cut at ground level or within several inches of the ground, to prevent seed production. If stems are cut too high, the plant may produce additional flowers at the base. Once seedpods are present, but before the seeds have matured or scattered, the stalks can be clipped, bagged and trashed to prevent continued buildup of seed stores. This can be done through much of the summer.
Be conscious of erosion and soil disturbance caused by clearing land. See Land Disturbance.
When a plant is very well established, the safe use of regulated herbicides is often the most practical method to remove an invasive plant population. When using any herbicide, pesticide or lawn chemical, it is essential to carefully read and follow the label instructions. Make sure the correct chemical is applied in the correct amount and is intended for the plant to be removed.
Remember, the Label is the Law
When a plant is very well established, the safe use of regulated herbicides is often the most practical method to remove an invasive plant population. When using any herbicide, pesticide or lawn chemical, it is essential to carefully read and follow the label instructions. Make sure the correct chemical is applied in the correct amount and is intended for the plant to be removed. THE LABEL IS THE LAW.
County agencies and the Fairfax County Park Authority implement the use of herbicides and pesticides for the management of invasive species as part of an integrative pest management strategy. When mechanical methods are not an option, the use of chemicals are carefully prescribed on a site-by-site basis. Only contractors and staff who are registered technicians or certified applicators through the Virginia Department of Agriculture and Consumer Services (VDACS) may apply herbicide on public lands. Land managers evaluate the extent of the problem, consider rare species, sensitive ecosystems, cultural resources and clearly define site goals to identify those target species that interfere with the goals of each site. County and FCPA staff abide by all Department Environmental Quality (DEQ) regulations and guidelines and apply herbicides and pesticides by Environmental Protection Agency recommended standards as listed on each label.
To manage certain invasive species in natural areas, herbicide is a necessary tool from the toolbox for habitat restoration and protection. Park Authority contractors install signs when they are treating invasives with herbicide and stay onsite until the herbicide is dry. Staff and contractors use herbicides appropriately and safely according to the label.
Find more information at Control and Management Resources, Blue Ridge PRISM Inc or the Managing Invasive Alien Plants in Natural Areas, Parks, and Small Woodlands, Department of Conservation and Recreation.
Foliar (Leaf application)
This method applies herbicide to the leaves of the plant. It is effective for woody or herbaceous plants in either spring when desired plants are dormant or in the late summer and fall when the plant is sending nutrients to the roots. In general, using an herbicide found in a gardening or home improvement store with the active ingredients glyphosate or triclopyr on the label will be effective.
Cut-Stem/Stump Treatment
This method is used on woody species for a small infestation or where leaf application may damage preferred plants. It is best used in the fall when the plant is sending nutrients into the ground to prepare for winter.
Basal Bark (at the base of the tree)
This method is effective throughout the year for woody plants when the ground is not frozen.
Hack and Squirt
This method is effective throughout the year for woody plants when the ground is not frozen.
Injections
Injection methods, injects a small amount of pesticides or herbicides into the tissue under the bark of the tree or into the stem of a plant. It is a more precise treatment and may reduce the quantity of chemical used.
Biocontrol is the use of organisms for control of a pest species. For example:
Fairfax County and Park Authority partner with state and federal agencies for the use of biocontrol agents. Residents are not permitted to release organisms onto parkland without permission from Park Authority staff.