I suspect this may be one of the avens (the genus Geum) based on the leaf structure. This genus is in the rose family and the species I know are natives. Many of the avens tend to be kind of weedy, although they often have pretty white or yellow strawberry-like flowers. Geum triflorum is one of my favorites (I don't think your example is that species) and definitely (in my book) G. triflorum is NOT a weed. G. triflorum is called prairie smoke and has reddish purple flowers that really don't look like a strawberry flower, but end up producing seeds with really long feathery hair. If you have a mass of these, it ends up looking like a cloud of pinkish smoke when the plant seeds. Very cool. I also think your client can watch for this plant to bloom and with flowers, someone should be able to provide you with a more definite ID.
Brian (:))
