Growing with a Crataegus sp., which was there first and is the most common woody species along the fence line and slope. Although I don't know how old this specimen is, it appears to have been there a while, which makes it interesting that R. cathartica is not common in there. In fact, this might be the only one of the species growing in that area on both sides of the creek and at least ~100 m upstream of Gerber Rd (see map). This, of course, doesn't mean its growth and potential spread shouldn't be controlled.