Poison ivy can and does take on a few forms as it grows and matures. In its smallest form, it sprouts from seed into a seedling that quietly grows in the understory or at the edge of the woods. Later as it becomes more established, poison ivy can become a rambling vine growing along the forest floor or the brush next to your mowed lawn.
While it is still young, you can find it with dull or shiny leaves with some red tinge to them. Poison Ivy does not seek out places to climb, it does take advantage of fences, and small and medium sized shrubs. Without a shrub or fence to grow on, it can grow together creating a shrub on its own.
When poison ivy comes upon a tree, it will change form yet again. As the vine begins to grow up the trunk, the vine creates aerial roots anchoring the vine to the trunk. The sky is the limit in terms of how high it will climb. Old established vines can be several inches in size and each leaf can be quite large, confusing us in identification. As a climbing vine up the tree trunk, the last phase of growth becomes reproductive with flowers and berries with seeds inside.
When you find poison ivy in the yard, it likely will be the young plant just starting out or at the start of vining. One of the best things you can do is show and teach every family member what it looks like so it can be avoided. Not everyone has the same sensitivity or reacts the same, but everyone should know what it looks like and where in the yard it is. Remember, the leaves are in sets of three.
Whenever you work around poison ivy wear plenty of clothes to protect your body. The oil in the stems and leaves causes the dermatitis. In the winter, you can use pruners and carefully cut it out of shrubs or cut and remove the vine as it crawls along the surface. Even in the winter, you can get a mild case of dermatitis from the little oil left in the stems and vines. There are chemical treatments available for controlling this plant. Since it is a woody plant, it will take more time to get it under control and repeated applications are often needed. Read those labels carefully, as some products may only "suppress" poison ivy.