Poison Ivy is in the Anacardiaceae family, which also includes cashews, mangos and sumacs. The sap of the stems, roots, fruit and leaves of many species in this family contains urushiol oil, which is what causes the allergic rash in 80% of humans that come in contact with these species. Poison Ivy is very sensitive to carbon dioxide, and even slightly elevated levels of CO2 have proven to increase its growth. In the past 50 or 60 years, during which time the amount of carbon dioxide in the atmosphere has increased by roughly 22%, Poison Ivy’s growth rate has doubled. The amount of urushiol oil has not only increased, but it is also more potent…leaves of three, let them be.
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