Poison ivy - you know you don't like it, but what do you know beyond that? Roughly 85% of people are allergic to poison ivy (10-15% severely so) which makes this plant the arch-nemesis of many a gardener. Today we take a look at how to identify it, how to avoid getting a rash, how to treat a rash if you do get it, and how to kill the plant.
Let's start with identification. Poison ivy has compound leaves that always have 3 leaflets (see photo on left). This means that each leaf stem has three tiny leaves attached to it (my mom always used the the rhyme "leaves of three, beware of me"). There is often a reddish color on the leaf stem, although it's not always prominent. Poison ivy creeps along the ground or climbs up plants and structures, and it never stands straight up on its own. For information about poison ivy look-alikes and how to tell them apart, check out this comprehensive post from another blog or this quicker post with two common impostors from our friends at Keep Indianapolis Beautiful.
The best way not to get poison ivy is obviously to know how to spot the plant and avoid touching it, but sometimes you don't see it until it's too late, or you don't notice it at all. Fortunately, if you do touch poison ivy there are ways to avoid an itchy rash. It is the oil secreted by all parts of the plant (urushiol oil, if you want to get technical) that causes the allergic reaction. It acts like a stubborn grease on your skin, so the key is to use the same kind of tactics you might use to get grease off your skin: soap, cold water, and scrubbing action. The scrubbing is essential. It's more effective than soap, so if you don't have soap on hand just find whatever you can to scrub the skin - whether it's a towel or a handful of wet sand. This popular YouTube video demonstrates how to get off poison ivy oil using axle grease to visualize urushiol oil. If you have been in the woods or in any other place where you suspect you may have come into contact with poison ivy, it's a good idea to immediately wash your clothes and thoroughly clean your skin. Cold water is better than hot water because hot water will open your pores and make it more likely that some of the oils will be absorbed.
If you do get poison ivy, there are all sorts of products that help. Calamine lotion is a classic that will soothe the itch and help dry out the rash. Hydrocortisone-based anti-itch creams relieve itching. Benadryl cream or other antihistamine creams help block the molecules that drive the allergic reaction to stop itching. Lotions that have menthol mixed in provide an instant cooling effect while the rest of the active ingredients kick in. Oral antihistamines can help as well. If I have an especially nasty case that's driving me crazy, I take Benadryl at night for the combined anti-itch and sleep-inducing effects. Oatmeal baths can soothe the skin, as can cool compresses. If you're interested in more natural remedies, check out this list.
Now for my favorite part: killing poison ivy. Pulling it out by the roots is the most immediately effective method. If you know someone who isn't allergic, ask them to pull it for you. If not, you can pull small weeds by putting a plastic bag over your hand, pulling the weed with the bag, and then closing the bag (the same concept as picking up after your dog on a walk). For bigger plants, you'll just have to dress to for minimal skin exposure and wash thoroughly afterward (if you didn't already watch the YouTube video I linked to before, watch it before you try this). If you want to go the herbicide route, make sure you use a systemic herbicide like RoundUp that will kill the roots. You may need multiple applications, and if you're dealing with a large plant you have to get the whole thing. If a vine is climbing through another plant, you need to cut the vine where it starts to climb the other plant and then spray the poison ivy where it's in the ground. It is not good to spray the trunk or branches of a tree with herbicides. The down side to using chemicals to deal with poison ivy is that you then have a bunch of dead poison ivy to deal with, and there are still residual oils on the dead plant that can cause a reaction. Use the same care when removing dead poison ivy as you do when dealing with live plants.
I'm going to end on a note sympathetic to poison ivy. Yes, this plant does have a redeeming quality. It is a native plant, and its berries are a great food source for wildlife. I'm not by any means saying that you should let poison ivy run free on your deck, but if you are dealing with a natural area where little human traffic is expected, consider letting it be. You can avoid the headache of trying to kill poison ivy in its natural habitat (trust me - it's not easy), and you can feed the birds at the same time. I hope you now feel more prepared to deal with this dreaded plant. Knowledge is power! We have focused on poison ivy for this post since it's the most common, but the same information applies to poison oak and poison sumac (except for the plant identification). Hopefully this information will help you enjoy the outdoors itch-free this summer.