After a little due diligence, we found that there is an invasive Aralia: Aralia elata or (Japanese Angelica Tree). The two are very similar, and one of the best ways to tell the native from the invasive apart is by waiting until it flowers (which of course can wreck havoc on your control efforts). The flowers of the invasive plant tend to be surrounded by the leaves, and have no distinct central axis whereas the flowers of the native plant have the base elevated above the leaves, and does have a distinct central axis. All other characteristics are variable and are not always useful in determining species. Based on the invasive tendencies shown by the plant on our walk, we are secure in identifying it as the invasive Aralia elata.
Based on its tendency to spread through its roots and seed source, similarly to Ailanthus Altissima, similar control techniques should work well on the plant. Smaller populations can be hand pulled, but the larger plant should be cut and the stump should be immediately painted with a non-dilute solution of glyphosate in the "cut-stump" method. The larger trees can be treated by drilling holes throughout the bark and filling the holes with the non-dilute solution of glyphosate.
Given the prominence of the Aralia elata throughout the landowner's property, we predict that the original plant that was identified as Tree Of Heaven was probably this invasive: Aralia elata. Hopefully this first encounter with the plant in Chester County, will be the last--but at least now we know what we are looking for, and will try to control it before it becomes more of an issue.
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