Article Credit: Zanfel www.zanfel.com
Poison ivy is a woody shrub or vine (ground vine or climbing vine), that sometimes seems to appear, almost magically, in our yards and gardens. Poison ivy is a dioecious species (meaning individual plants are either male or female). One study done by a horticulturist in the Philadelphia area found that a mature female poison ivy vine can produce as many as 30,000 seeds each year!
These seeds are contained within berries which start out as green in summer, and then turn an ivory color by the end of the growing season. These berries are high in fat content and the birds know it. They are eaten by both migratory birds and over wintering birds, who spread the seeds all over in their droppings.
Poison ivy seeds are spread almost exclusively by birds. This is why poison ivy plants are less likely to be found growing out in open areas. They are more likely to be found growing under places where birds eat, and where they perch: your fence, under your trees, under bird feeders, and in your garden. Anywhere that birds hang out is where plants have a chance to get started.
All of this means that gardening and yard work are the most frequent activities that result in poison ivy exposures and subsequent allergic skin reactions. Activities like weeding, brush clearing, and pruning can break open poison ivy stems, releasing more of the poison ivy plants' oily allergen, urushiol. When larger amounts of urushiol are absorbed into a person's skin, the result is a more severe allergic skin reaction.