After we moved to our little 3-acre bit of the world, I had poison ivy rashes about 4 months of the year. The photos I had seen didn't really help much with prevention.
Finally, when I took the Master Gardener class, Sue Gray taught us how to identify it and now I rarely have a problem. Also, when I'm weeding around trees in the woody areas, I use a poison ivy soap immediately after.
Keith Kridler of Mt. Pleasant TX talked about Poison Ivy on Daffnet recently -
"This vine creeps along the ground until it finds either a tree or wall or fence that it can attach anchoring roots to and within a few years the vine will be at the very tops of the tallest trees. Once the vine matures it begins to bloom profusely attracting all sorts of native and non-native pollinators to the high percent of the sugars in the nectar, but this nectar comes from minuscule blooms.
In the fall there are tens of thousands of BB sized white fruit on these vines. The fruit is eaten by over 40 species of birds during migration and these birds digest the fruit surrounding the seeds. The seeds pass through the gut of the birds and often get dropped hundreds of miles from the mother vine creating many more vines the following year.
While it is a tremendous asset and food and nectar source for wildlife the milky white sap contained inside EVERY part of this plant will create a profusion of boils, blisters and open sores once it gets inside the human body. Burning of the leaves and or woody vines or even the roots of this plant and then inhaling the smoke will create massive damage to the lungs of a human.
These leaves vary in color from vine to vine or probably from different locations and depending on the composition of the soil these leaves will be canary yellow, flaming orange, screaming candy apple red or the darkest, deepest shades of maroon, practically a blue black red on occasion.
We gardeners must be aware that when weeding our flower beds that there WILL be sometimes hundreds of these new seedlings sprouting in the rich soils we created for our flowers."
from Absolute Astronomy -
Various mnemonic rhymes describe the characteristic appearance of poison ivy:
1."Leaves of three, let it be."
2."Hairy vine, no friend of mine." Poison ivy vines are very poisonous.
3."Raggy rope, don't be a dope!" Poison ivy vines on trees have a furry "raggy" appearance. This rhyme warns tree climbers to be wary. Old, mature vines on tree trunks can be quite large and long, with the recognizable leaves obscured among the higher foliage of the tree.
4."One, two, three? Don't touch me."
5."Berries white, run in fright" and "Berries white, danger in sight."
6."Longer middle stem, stay away from them." This refers to the middle leaflet having a notably longer stem than the two side leaflets and is a key to differentiating it from the similar-looking Rhus aromatica - Fragrant sumac - is a plant species in the family Anacardiaceae native to Canada and the United States.Fragrant Sumac is a woody plant that can grow to around 2 meters tall. It produces yellow flowers in clusters before anthesis...
7."Red leaflets in the spring, it's a dangerous thing." This refers to the red appearance that new leaflets sometimes have in the spring. (Note that later, in the summer, the leaflets are green, making them more difficult to distinguish from other plants, while in autumn they can be reddish-orange.)
8."Side leaflets like mittens, will itch like the dickens." This refers to the appearance of some, but not all, poison ivy leaves, where each of the two side leaflets has a small notch that makes the leaflet look like a mitten with a "thumb." (Note that this rhyme should not be misinterpreted to mean that only the side leaflets will cause itching, since actually all parts of the plant can cause itching.)
9."If butterflies land there, don't put your hand there." This refers to the fact that some butterflies land on poison ivy, since they are not affected, which provides them protection as their predators avoid eating the plant.
10."If its got hair, it wont be fair" This refers to the hair that can be on the stem and leafs of poison ivy.
Whatever device you use to identify its many colors, forms, leaf shapes, stem shapes or colors, be sure to keep your hands away from it. For those of us who are allergic, the rash is very itchy and lasts for weeks.