The taxonomy of J. communis is rather messy. There are several distinct varieties, but great phenotypic plasticity has also lead to multiple names being applied to a single variety. Robert Adams (http://juniperus.org/
) has made a career studying Juniperus, and he has done a good bit of genetic work on J. communis. J. c. var. communis is widespread in Europe and apparently diverged from most North American populations a few million years ago. Variety depressa is by far the most widespread in N America with individuals from North Carolina, the shores of Hudson Bay, and Danali National Park in Alaska showing strong genetic similarity. There are other varieties in N America: a large fruited variety in Labrador or Newfoundland, var. jackii in the northern Pacific Northwest, and an undescribed variety that grows in muskegs in Alaska; however, var. communis is not known from N America.
The site in NY where I measured J. communis has spreading bushes as well as columnar individuals. One plant bushy plant even had a single branch that had turned vertical and was rapidly elongating. J. communis seems like a good example of a species that can drastically alter its growth form depending on growing conditions.