Until you can easily ID poison ivy, the adage of "Leaves of Three Let It Be" are pretty good words to live by. Mature poison ivy provides the birds the berries that later are deposited along fence rows, beneath deciduous and evergreen tree canopies, and shrub borders.
As a small seedling, they look like many other immature weeds, not quickly recognizable. As they grow the characteristic three leaves begin to develop. This is one of the forms and stages we find poison ivy, a typical weed in the garden.
As the seedling continues to grow, poison turns into a vining growth habit for its next form with the leaves clearly looking like all the pictures we see of the three leaves. As a vine it can easily be hiding in a bed of ground covers, reaching out into the lawn from the edge of the woods, climbing up the house wall with the Boston ivy or other ornamental vines. Gardeners will also find it while pruning their shrubs in the shrub canopy.
If the poison ivy vine runs into a tree trunk, then the third form shows up as vine that can cling to the bark using brown aerial roots. This form as a vine climbing the tree becomes the mature stage where well up in the tree canopy, poison ivy has very large leaves again with the typical three leaflets, but those leaves may be two feet in size. Besides the gigantic leaves, this is where and when it begins to flower and fruit, setting the repeating cycle in motion. In the fall all those vines we see in the forest preserves and woods with our common areas can be combinations of poison ivy and other native vines. Poison ivy has outstanding reds for a fall color and is quite attractive, just look and don't touch.
In the home landscape removing poison ivy while small and before it begins to vine is best. It is the oil in the plant that gives us the dermatitis. Watery blisters are common. As a young seedling they will die if pulled out and left to dry handling them as little as possible. You can use a digger of your choice for this so you do not come in contact with the plants. Wearing an unlined rubber glove is a good idea too. With plants slightly bigger, gardeners could use a glyphosate product, but very carefully around valuable ornamentals. Using a small paint brush or trim roller can be very helpful. If it is in a shrub, cut it off at the ground and let it completely dry before attempting removal. Treat the stump of the vine as well. If you find yourself with one of those vines up the tree, carefully cutting through the vine is the best option. Do not remove the vine; just leave it there to dry in the tree without the need to pull it down. Treat that vine stump too. Vines growing up the tree can be as small as a quarter of an inch to over 3 inches in diameter for a larger mature vine.All parts of poison ivy can give you dermatitis; you can get a reaction to poison ivy even in the winter when plants and vines are dormant. NEVER burn poison ivy as the oils will be in the smoke!