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I've got a bunch of poison ivy growing up a tree. I'd like to kill the poison ivy, but obviously not the tree it is growing on.
It is just about impossible to spray the ivy without hitting the tree, but I was curious as to whether it will harm the tree if I just get it on the bark and not the leaves.
I realize it is probably safest not to do this at all, but I was just curious how these herbicides work.
To answer your question directly, it depends entirely on the type of tree and the type of herbicide. It might be okay, but it might not be. It is possible to kill a tree with herbicides, and it is possible to kill poison ivy on its own with certain herbicides without killing certain trees.
Unless you're prepared to be absolutely certain that the type of herbicide you're using isn't going to harm a tree you care about, it's probably a safe bet to skip it. There's nothing that a pick axe + hoe + gloves can't solve. Rip the suckers out!
One method that I've heard of but haven't tried myself is to cut the vine and apply herbicide directly to the cut. That way you minimize collateral damage.
They do make a chemical just for poison ivy but I'm not really sure what else it kills. Beyond that you could try to treat some of the leaves with it and slowly kill it. I had to do this with some trumpet vine growing in with some roses, it worked but it took a while.
Cont forget to wear some sort of disposable glove too, that way you can touch the ivy and not get it! Nasty stuff.
It entirely depends on which herbicides you use. For example, Glyphosate is commonly used in Round-Up and Rodeo products and is not selective on which plant it kills. Triclopyr is another popular one but can also affect wooded plants.
If you're very concerned about the tree, you'll likely need to speak to a professional or find another way to extract the ivy.
Cut the ivy off at the base of the vine and immediately paint undiluted Glyphosate (Roundup) on the cut surface above the roots. This herbicide is systemic and will kill the roots. Be careful not to spill it around the roots of the tree however. keep an eye on the area to make sure no more ivy grows. Repeat the process if necessary. You can let the upper vine die off naturally. Be cautious with handling dead material as it will still give you a rash. I'm a landscaper and have found this technique works very effectively with lots of undesirable plants: bamboo, poke, escaped wisteria and other vines. Tedious but I find I seldom have to treat again.
I can't answer your direct question, but to build on other suggestions - instead of just cutting off the vine and painting herbicide on it, get a container large enough to hold several feet of vine (e.g. a milk jug). Feed the vine into it, then fill it with herbicide. This will avoid any overspray on the tree, but also let the entire vine & leaves "drink" up the herbicide and hopefully be more effective than just painting the end of the vine.
