Weed Of The Month: Poison Ivy
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Weed Of The Month: Poison Ivy Allison Kosto, MSU Broadwater County Extension Agent The Montana Field Guide shows that there is Poison Ivy in Broadwater County. However, growing up here and even as an adult, I have never seen it nor had anyone submit a sample to the office, until recently. Finally, last summer we found it. It is likely not the only patch but I can confirm a large patch in the Crow Creek Valley along Warm Springs Creek. It’s definitely something to keep an eye out for, although not extremely common in our area.
Description & Habitat Western poison ivy is native to North America. It does not have some of the same environmental concerns as other “weedy” species. However, it does cause concern due to its toxicity to humans. A simple touch of the plant can cause skin blotches and burning blisters which can cause swelling and intense pain.
Poison ivy is a small shrub that can be 4 to 20 inches tall. It is commonly found in fencerows, along creeks, roadsides and woodlands. The leaves are shiny, and each leaf is made up of three leaflets. In the fall, poison ivy has a vivid reddish color that makes it attractive. The flowers are not often visual underneath the leaves. Fruits are greenish-yellow and occur in clusters. The plant is primarily spread from seeds dispersed by birds who eat the fruit.
All parts of poison ivy contain resinous compounds called urushiol which cause inflammation, itching and blistering when they come in contact with the skin. About 80% of people are sensitive to the toxin and have an allergic reaction to the plant. This liquid can also get on tools, pets or clothing and then transfer to skin indirectly. Dead plant material also contains urushiol. They can even become a gas when poison ivy is burnt. If you are exposed to poison ivy, wash immediately with soap and water. Contact a medical professional if you inhale smoke from burning plants, have large areas of skin exposed or need symptom management (itching, swelling, etc.).
Management Proceed with caution when controlling or eradicating this plant. Make sure no skin can be exposed to the plant by wearing gloves, long pants, socks, shoes and a long-sleeved shirt. Wash any clothes that come in contact with poison ivy after working around the plant. Never burn poison ivy.
Digging and pulling have been shown to be effective. You may have to do it more than once though if not enough of the root system is removed. Another management option is the use of goats as biological control. They can help suppress or stop the spread of the plant, but may not fully eradicate it.
Herbicides are also an option. The best active ingredients for poison ivy are glyphosate, 2,4-D or triclopyr. Examples of brand names are 2,4-D Amine, Basecamp, Crossbow, Garlon, and Remedy. 2,4-D is best applied in late spring or early summer when plants are actively growing. Triclopyr is best in early spring or in the fall before leaf color changes. Glyphosate (i.e. Roundup) is a nonselective herbicide that will also kill desired plants. Always read and follow the entire label when applying herbicide. Common chemical names are used for clarity but does not imply endorsement of a product or brand.
For assistance on weed identification and management, contact the MSU Extension Office in Broadwater County at 406-266-9242.
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PhotoCredit: Allison Kosto
Image 1 Caption: poison ivy
