Tuesday, June 16, 2009

Poison Ivy

As I drove into our office complex today I noticed a member of the grounds crew cleaning up stems that had been sheared from a privet hedge. Most of it was privet, but I also knew that there was plenty of poison ivy in there, too. I had been observing it for a few weeks, thinking about the challenge of killing poison ivy that is entwined in landscape plants.

I stopped and chatted with him to be sure that he knew what he was dealing with. Sure enough, his arms were blistered up from previous encounters with this weed. We shared remedies for the itch, methods to control the weed and ended up wondering if there was anything positive about poison ivy. I know that bees and other insects collect its nectar and pollen; birds eat the seed. The grounds man thought there might be some therapeutic, whole-body effect from having the rash… what a great attitude!

Poison ivy, Toxicodendron radicans, is a native, perennial, woody vine that is the major cause of allergic dermatitis in the Eastern U.S. according to Weeds of the Northeast, (Cornell University Press). It is very commonly found in Pennsylvania and easy to identify, despite the fact that its leaf characteristics vary somewhat, depending on where it is growing. “Leaflets of three, let it be”, is a saying that begins to draw your attention to key characteristics. The center leaflet extends on a relatively long stalk. The upper surfaces of the leaves are often quite shiny, especially when growing in full sunlight. The leaflets are usually lobed or coarsely toothed. Mature plants climb trees with the aid of aerial rootlets and the older stems become rope-like and quite hairy. But poison ivy is often found running along the ground in the forest understory, and there, the leaves are dull green. Both the newly emerging spring growth and fall foliage are red. Contact with any part of the plant causes a skin rash in most people.

Since poison ivy is perennial, it is not easily controlled by mechanical methods such as mulching, pulling or mowing. In woods and other unmanaged areas, just learn to recognize it and enjoy its beauty in all seasons. If it is growing in places where you or others (unsuspecting kids) are likely to bump into it, you can control it chemically.

Two herbicides, glyphosate (sold a Roundup and many other trade names) and triclopyr (Sold as Brush-B-Gone and others) will kill poison ivy. I think triclopyr is most effective. Glyphosate products will kill or injure any green plant that it contacts. Triclopyr will not injure grasses and this may make it useful in some settings. Both products are applied to the foliage of target weeds. In fact, healthy weed foliage is important for maximum uptake and translocation of the herbicide. Neither product is root absorbed so you can be quite selective by applying the herbicide only where you want it. As long as desirable plant foliage is not contacted it is safe from injury. Read the labels for complete instructions.

So, before the year is over, and once the poison ivy re-grows from the hedge (which it surely will) I hope to help the grounds crew selectively and carefully wipe one of these herbicides onto the poison ivy growing in the privet, avoiding all privet foliage.


Anonymous said...

Hi, I am the community outreach coordinator for the WV Poison Center, and I liked your post about poison ivy. We get calls from people who have been exposed to it. This summer, I got a bad case by petting my dog, who had apparently gotten into poison ivy in the yard. My brother cut all the branches where it came out of the ground, so the foliage would die. Then, I happened to think the dried up leaves might still have urushiol on them. What do you think?
Kim Fetty

Scott Guiser said...

I wish I new more about poison ivy and ability to cause rash after leaves have dried. I don't know. Poke around on the internet at reputable sites and you will probaly find an answer. Sorry.
PS I would say that drawing a conclusion about how you got exposure can be tricky. For instance, if you walk thru it and then handle shoes/boots you may be exposed and then blame the poor dog!