Jason -
Excellent question. The answer is that dead leaves which have fallen naturally from the vine are harmless. As the leaf dies off, the urushiol oil is pulled back into the vine. Here's a link to an excerpt from Susan Hauser's book: Outwitting Poison Ivy: How to Prevent and Treat the Effects of Poison Ivy, Poison Oak, and Poison Sumac--For Hikers Campers, Gardeners, and Anyone Else Who Spends Time in the Outdoors. If the leaves are broken off or do not die off naturally, then those are still toxic. Poison ivy is a deciduous vine and so there will be leaf litter each year.
Now for leaves that have not fallen off naturally, these will still have urushiol oil. The same issues exist here - how long the oil is potent is variable due to a number of factors including environmental conditions (heat, humidity, etc.). Most texts quote about a year for urushiol oil to be potent on items such as garden tools so it would follow that this could also be a legitimate timeframe for those leaves. |
