Manage Poison Ivy Safely

Poison ivy (Toxicodendron radicans) is one of the most challenging native weeds found throughout Pennsylvania. Its ability to grow as a groundcover, climbing vine, or sprawling shrub makes it difficult to manage. This notorious perennial plant contains urushiol, an oily substance that causes an allergic skin reaction in most people. Even dead poison ivy plants and roots retain active urushiol, making their removal hazardous for years.

Identification

Another native vine, Virginia creeper (Parthenocissus quinquefolia), grows in similar locations. A Virginia creeper leaf always has five leaflets, while poison ivy possesses only three leaflets. Remember the rhyme, "Leaves of three, let it be; leaves of five, let it thrive!" to help distinguish between these two plants.

In early spring, the new leaves of both plants are reddish, then mature to shiny or dull green. In autumn, the leaves turn to beautiful shades of red and orange. The margins, the leaflet edges, of poison ivy can be smooth, wavy, or coarsely notched.

Eastern poison oak (Toxicodendron pubescens) is a plant of coastal soils. Poison oak may grow in the southeast corner of Pennsylvania, but it is uncommon elsewhere in our state. Its leaflets tend to be more rounded and lobed, like oak (Quercus spp.) leaves. Usually, the leaves have fine fuzz on the undersides. This plant tends to be more shrub-like. Stay away from it as all portions contain dermatitis-causing urushiol.

Harmless staghorn sumac (Rhus typhina) is frequently blamed for the dermatitis caused by poison ivy growing beneath it. Staghorn sumac has fuzzy stems and toothed leaflet margins. Poison sumac (Toxicodendron vernix) has smooth stems and leaflet margins. Poison sumac is an obligate wetland plant that grows in swamps, marshes, and soggy habitats that humans rarely visit.

Mechanical and Cultural Control

Mechanical control is physically removing or suppressing poison ivy without using chemical herbicides. It is labor-intensive, but preferred in environmentally sensitive areas, near water features, around valued plants, or where pesticide use is not allowed.

Personal protective equipment (PPE) is essential, including long-sleeved shirts, long pants, closed-toe shoes with socks, waterproof gloves, and protective eyewear. Disposable nitrile gloves worn beneath heavy-duty work gloves provide protection. Every part of the poison ivy plant, including its roots and underground spreading rhizomes, should be removed because poison ivy readily regrows from even the smallest bits of root. Never compost or burn this plant material. Burning poison ivy creates smoke filled with urushiol particles, which will irritate exposed skin and burn the lungs if inhaled. Bag and dispose of the poison ivy in the trash.

Hand-pulling is effective for small infestations, especially when plants are small and the soil is moist. Digging is often more successful because poison ivy develops extensive rhizomes. Use a digging fork or shovel to remove roots down to several inches. Monitor often, as missed root pieces will produce new shoots.

Cutting and mowing provide only temporary suppression. It takes several growing seasons of careful trimming, but eventually, root reserves may be depleted. Mowing causes leaf pieces laden with urushiol to spread throughout the area. String-trimmers may produce airborne particles of urushiol-containing sap!

For poison ivy vines that have climbed on trees, create a "window cut." Cut the vines near ground level and again several inches above the first cut. If possible, remove the severed section. Allow the upper section of vines to die naturally. Pulling large vines from tree trunks damages the bark and exposes the worker to significant amounts of urushiol.

Mulching can suppress young poison ivy seedlings. Applying 3 to 6 inches of wood mulch can reduce germination and limit growth. However, established plants will emerge through the mulch. Smothering with cardboard, landscape fabric, or heavy black plastic works on localized patches. The covering must remain in place for an entire growing season or longer. Monitoring is essential because poison ivy can emerge through small openings or around the edges.

Goat grazing is sometimes used to suppress poison ivy. Unlike humans, goats are unaffected by urushiol and readily consume poison ivy foliage, but not the roots. Repeated browsing (as with cutting and mowing) is required. Be aware that goats do not distinguish between plants we consider desirable and those we consider undesirable.

Organic Herbicide Options

Organic herbicides are derived from naturally occurring substances. While many homeowners assume these materials are safer and more effective than synthetic herbicides, organic herbicides have significant limitations. The instructions and signal words on some organic weed killers indicate that more PPE and greater care are required than on some synthetic herbicides!

Most organic weed killers are contact herbicides, meaning that they injure only the plant tissues that they touch. Common active ingredients include acetic acid, citric acid, caprylic acid, clove oil, cinnamon oil, and other plant-based compounds.

Horticultural vinegar products containing 20-30% acetic acid can burn poison ivy leaves and stems. Unlike household vinegar (5% acetic acid), which does not affect plant tissue, horticultural formulations cause rapid browning and defoliation, but the roots remain unaffected.

Similarly, clove oil-based herbicides disrupt plant cell membranes, with visible injury occurring within hours. Citric acid products cause tissue desiccation, resulting in leaf burn.

Organic herbicides are most effective on young seedlings, recently emerged shoots, and small infestations. Large, mature vines with their extensive root systems often survive treatment. Repeated applications to the top growth are required every two or three weeks during the growing season.

Despite their natural origins, organic herbicides are not risk-free. Concentrated acetic acid causes chemical burns, permanent eye damage, and respiratory irritation. Its signal word is "DANGER – CAUSTIC". PPE is essential during application.  Always read the entire label and especially note the signal word. 

Synthetic Herbicide Options

Synthetic herbicides generally provide the most reliable and cost-effective control of established poison ivy infestations. The most effective products are systemic herbicides. They are applied to the foliage and move (translocate) from the leaves down the stems into the roots, killing the roots.

Proper timing is critical. Apply herbicides when poison ivy has sufficient healthy leaf area to absorb the product. Drought-stressed plants may respond poorly. Monitor to determine if root fragments survived. Synthetic herbicides often require fewer applications than organic products. Remember, the label is the law! Follow all label instructions for application, PPE, and environmental precautions.

In 2022, Bayer changed the formulation of its Roundup products. None of their Roundup products in the United States residential lawn and garden market contains glyphosate.

Glyphosate is still a commonly used systemic herbicide. Glyphosate is non-selective, meaning it affects all types of plants, both broad-leaved and grass-like.

Triclopyr is a selective herbicide. It affects broad-leaved plants like poison ivy but spares narrow-leaved plants, like grasses. Neither glyphosate nor triclopyr remains active in the soil. Many professionals consider triclopyr particularly useful for controlling mature poison ivy growing among trees and shrubs, when applied correctly.

2, 4-D is a systemic, selective herbicide that manages only broad-leaved plants, including poison ivy. It is a common ingredient in lawn weed herbicides. Apply it when leaves are fully expanded. Allow several days for the herbicide to translocate before mowing.

Glufosinate is a non-selective herbicide that acts primarily as a contact herbicide. It does translocate in very small seedlings to kill roots, but it rarely affects the roots of perennial plants enough to kill them.

Another method of managing woody vines and shrubs is the cut-stump method. Rather than spraying the foliage, use pruners or a hand saw to cut the woody stem just above the ground, and immediately (within 15 minutes) apply a concentrated systemic herbicide, like triclopyr or glyphosate, to the living tissue of the cut stump. It must be the concentrated herbicide, usually 20 to 45%, not the ready-to-use or ready-to-spray product concentration. The herbicide will translocate to inhibit sprouting. This technique is especially effective for poison ivy vines climbing tree trunks. When cutting the vine, take care not to damage the bark on the tree trunk. Make a second cut to the vine about 1 foot higher. Carefully remove the vines from this "window cut". Allow the upper vines to die naturally. Do not pull them down, as that will cause bits of urushiol-filled aerial roots to fall. Vine removal can damage the tree's bark. Monitor the cut stumps at the base for sprouting. This technique does not work well in the spring when sap is naturally flowing upward from the roots. The cut stump method works best from late summer through autumn because at this time of the year, nutrients are flowing downward from the leaves to the roots to store energy for the next season's growth. The systemic herbicide easily moves downward to impact the root system. 

Dangers of Homemade Weed Killers

Social media posts and internet articles frequently promote homemade weed killers containing dish detergent, table salt, Epsom salt, household vinegar, or chlorine bleach. While these mixtures may temporarily injure plants, they present significant risks. They are neither natural nor organic.

Dish "soaps" are not true soaps; they are detergents, synthetically produced and chemically designed for cleaning grease and food residues, not for use on plants. Insecticidal soaps are specially formulated to manage insects without damaging plants. Note that these insecticidal products contain soap, whereas dish-cleaning products contain detergents and additives. Detergents can alter soil properties and harm beneficial microorganisms. Dish detergent ingredients also persist in the environment. Some are even carcinogenic! None has been evaluated for routine landscape application.

Table salt (sodium chloride) is among the most problematic homemade weed-control ingredients. Salt kills plants by disrupting water uptake and causing dehydration. High salt concentrations can prevent future planting and injure nearby trees, shrubs, turfgrass, and flowers. Salt also moves with runoff, affecting surrounding landscapes and aquatic ecosystems. Unlike pesticides, which are designed to degrade, sodium contamination persists.

Epsom salt (magnesium sulfate) can create nutrient imbalances in soil, interfering with calcium and potassium uptake. Despite widespread claims online, there is little scientific evidence that Epsom salt selectively kills weeds.

Household vinegar (5% acetic acid) may burn very young weed seedlings. Still, it does not provide control of perennial weeds such as poison ivy.

Chlorine bleach is one of the worst substances to use as a weed killer. Bleach is not labeled for vegetation management and can severely damage soil health. It is toxic to beneficial soil organisms. Bleach may react with other chemicals to produce hazardous gases. Mixing bleach with vinegar releases chlorine gas, while combining bleach with certain cleaners can generate other toxic compounds. Exposure causes respiratory distress, eye injuries, and skin burns.

Finish Safely

After working around poison ivy, remember to clean up safely to prevent the transfer of urushiol. Have trash bags ready for disposable PPE and paper towels. Urushiol remains active on tools for years. Wear fresh nitrile gloves when washing tools with warm water and detergent to remove the oil. Then rinse and dry well. Rubbing alcohol removes urushiol from pruners. Remember to wipe down the seat where you sat, as transfer from clothing is common. Thoroughly shower (bathing spreads existing oil) with cool-to-warm water and dish detergent to remove any oil from urushiol-laden plant bits that may have dodged the PPE.

Keep contaminated clothing separate from other household laundry. Launder contaminated clothing in hot water with laundry detergent on the longest cycle to remove the oil-based urushiol. Rinse with warm water twice. Afterward, run an additional wash cycle with laundry detergent in the empty washer.

Yes, poison ivy is an attractive native vine that provides fruits to feed the birds during the winter. However, when people brush against its leaves and contract dermatitis, it becomes the pest that needs to be managed. Follow our research-based advice and techniques. Manage it safely!

Resources

Homemade Pesticide Issues: Understanding the Science

UC IPM Statement on Homemade Pesticides

Home Remedies to Control Pests

Best Management Practices for Non-chemical Weed Control

Can I Use Vinegar to Control Weeds?

Vinegar: An Alternative to Glyphosate

Introduction to Weeds and Herbicides

Herbicides and Forest Vegetation Management

Cut Stump Herbicide Treatment