There is no pioson ivy growing in Oregon... most people mistake pioson oak for ivy, because it grow in three different forms, a small and manly leaf veriety that is in the shade or undergrowth, a large woody shrub in the open clearings, and a very devious vine that usally cralls up trees or better yet the side of a nice climb... the leaves of the vine like oak even resemble posion ivy leaves; as you mite guess it is mistaken for pioson ivy... another fact about the oak is that it dosn't grow above a sertain elevation, not sure exsactly how high but it is very evedent when climbing up a slope that is coverd with the baster brush and then all of a sudden it is never seen again untill you're on your way back down... have seen it when climbing up in the mountains? have you seen it when you are on the aproach to a wall in the lower valley areas? A very good way to avoid the nasty rash one might get is by observation... know your plants, it might just save you life some day...