Editing Toxicodendron radicans (section)

== Distribution and habitat ==
''T. radicans'' grows throughout much of [[North America]], including the Canadian [[Maritime provinces]], [[Quebec]], [[Ontario]], and all US states east of the [[Rocky Mountains]],<ref>{{BONAP |genus=Toxicodendron |species=radicans |date=2014}}</ref> as well as in the mountainous areas of Mexico<ref name="feis" /> up to around {{convert|1500|m|ft|abbr=on}}.<ref name=iucnredlist/> It is normally found in wooded areas, especially along edge areas where the tree line breaks and allows sunshine to filter through. It also grows in exposed rocky areas, open fields, and disturbed areas.

It may grow as a [[forest]] [[understory]] plant, although it is only somewhat [[shade-tolerant]].<ref name="feis" /> The plant is extremely common in suburban and exurban areas of [[New England]], the [[Mid-Atlantic states|Mid-Atlantic]], and the [[Southeastern United States]]. The similar species ''[[Toxicodendron diversilobum|T.&nbsp;diversilobum]]'' (western poison oak) and ''[[Toxicodendron rydbergii|T.&nbsp;rydbergii]]'' (western poison ivy) are found in western North America, and ''[[Toxicodendron orientale|T.&nbsp;orientale]]'' in Taiwan, Japan, Korea and Sakhalin.

''T. radicans'' rarely grows at altitudes above {{convert|1500|m|ft|abbr=on}}, although the altitude limit varies in different locations.<ref name="feis" /> The plants can grow as a shrub up to about {{convert|1.2|m|ft|abbr=on|frac=2}} tall, as a [[groundcover]] {{convert|10|-|25|cm|in|abbr=on|frac=2}} high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may be mistaken for tree limbs at first glance.

It grows in a wide variety of [[soil]] types, and [[soil pH]] from 6.0 ([[acid]]ic) to 7.9 (moderately [[alkaline]]). It is not particularly sensitive to [[soil moisture]], although it does not grow in [[desert]] or [[arid]] conditions. It can grow in areas subject to seasonal [[flooding]] or [[brackish water]].<ref name="feis" />

It is more common now than when Europeans first arrived in North America. The development of real estate adjacent to wild, undeveloped land has engendered "[[edge effect]]s", enabling poison ivy to form vast, lush colonies in these areas. It is listed as a [[noxious weed]] in the US states of [[Minnesota]] and [[Michigan]] and in the Canadian province of Ontario.

Poison ivy is particularly sensitive to [[carbon dioxide]] levels, greatly benefiting from higher concentrations in the atmosphere. Higher carbon dioxide levels increase the rate of plant growth, and cause them to produce more unsaturated urushiol, which causes stronger reactions in humans.<ref>{{cite journal |doi=10.1073/pnas.0602392103 |pmid=16754866 |pmc=1474014 |title=Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO<sub>2</sub> |journal=Proceedings of the National Academy of Sciences |date= 2006|first1=Jacqueline E. |last1=Mohan |first2=Lewis H. |last2=Ziska |first3=William H. |last3=Schlesinger |first4=Richard B. |last4=Thomas |first5=Richard C. |last5=Sicher |first6=Kate |last6=George |first7=James S. |last7=Clark |volume=103 |issue=24 |pages=9086–9089|bibcode=2006PNAS..103.9086M |doi-access=free }}</ref> Poison ivy's growth and potency has already doubled since the 1960s, and it could double again once carbon dioxide levels reach 560 ppm.<ref name="gazette">{{cite news|author=Templeton|first=David|date=July 22, 2013|title=Climate change is making poison ivy grow bigger and badder|url=https://www.post-gazette.com/news/health/2013/07/22/Climate-change-is-making-poison-ivy-grow-bigger-and-badder/stories/201307220149|url-status=live|archive-url=https://web.archive.org/web/20210726190537/https://www.post-gazette.com/news/health/2013/07/22/Climate-change-is-making-poison-ivy-grow-bigger-and-badder/stories/201307220149|archive-date=July 26, 2021|access-date=July 23, 2013|work=[[Pittsburgh Post-Gazette]]}}</ref>