Answer: Without seeing the weed, it's difficult for me to offer even an educated guess. Plants are identified by their flowers, growth habit, etc. I'd suggest digging a weed, roots and all, and either taking it to your local Cooperative Extension office, or the diagnostic lab at UMASS. You can mail it to the lab, if you want.
UMass Extension Plant Diagnostic Lab
Rooms 107-108, Holdsworth Natural Resources Center,
160 Holdsworth Way, UMass Amherst Campus, Amherst, MA.
Good luck with your garden!
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