Glyphosate in my woods By

[Danausplexippus]

I have been using glyphosate in my Woods to kill poison ivy 4 years. Question does using glyphosate as a foliar spray on poison ivy hurt the trees? Does the glyphosate seep into the soil get absorbed by the roots and end up killing or hurting the trees?

[RPF2509]

Glyphosate is not absorbed by the roots and is bound to soil particles by molecular attraction.  It is broken down by soil microbes in a few months as long as the weather is warm.  Cold weather slows microbial activity so it lingers longer during cold weather.  These characteristics are useful in choosing an herbicide.  It is active on the C4 metabolic pathway in grasses so if they are an issue, it is one of the few herbicides that will be active on grasses.  If you want to keep the grass, use a broadleaf only herbicide (c3 pathway) such as Garlon (trichlopyr) or 2,4-D.  Garlon with a bit of crop oil works well on poison ivy.  It does not have any soil activity either.  

[TreefarmerNN]

No matter what herbicide you use, I would be cautious about soaking a tree with it.  A little overspray likely isn't any big deal.  Soaking the bark can be as the active ingredient seeps into the cambium layer. 

[RPF2509]

Generally you need an oil based herbicide to soak through the bark.  Glyphosate can be used to treat larger stems through a stem injection or cut through the cambium and is effective that way.  Small amounts of glyphosate overspray can be damaging if it contacts leaves but will have no effect on stems.