Is this related to the project you posted in the landscape design forum several weeks ago?

Hemlock can be sheared as well as eastern white (EW?) pine, but if the shearing is stopped the resulting growth will be unattractive.

In the South, the conifers that will take part shade include various arborvitae, Eastern red cedar, Douglas fir, and spruces. The Eastern white pine isn't listed as taking much shade. The first two are pretty tight-growing, and can be trimmed. I don't know about the fir or the spruce. And I can't guarantee that this will be the same for you in MA.

I believe that the spraying program for wooly adelgids is easier done on smmaller trees, so might be feasible for the hedge on an annual basis, but as the trees in the back keep growing, it may be harder and harder to adequately cover them. Using different species for each might work better than having them both the same.

I would suggest that you contact your County Agricultural Extension agent - he/she should know what trees will grow under what conditions in your area. The spray program would also be in their area of experise.

Rhodium; Yes it is related to my landscape garden post. Their advice was not to plant anything due to a ROW. The amount of land cleared on the ROW for construction will not be nearly as wide as that needed once the pipeline is installed. If I don't landscape the area, it will re-forestate naturally, because I live near a thriving forest. I figured that I would speed along this process but in a landscaped manner using native trees and shrubs.
I'll post a picture of my plan.

Dibbet; Thanks for the info. I was thinking along the same lines. Spraying smaller trees/sheared hedges would be easier. I can't afford an arborist to spray a mature tree. With the tree sizes I'll be buying; however, those large size trees will be far in the future. I'll be doing some resarch on the spray types and consulting the MSDS.

Isabella