Answer: Unfortunately, I do not think your location is warm enough or sunny enough (on a northern exposure) to grow hollies. Your zip code places you in zone 5A or the coldest part of zone 5; depending on your microclimate could actually be gardening in a location as cold as zone 4. There may also be significant root competition from the pines. So overall I do not think this plan would work. Most evergreens need some direct sun to grow well and stay healthy and dense as we expect them to be. You might be able to grow yews there and clip them to a symmetrical or geometric form (these do not espalier but they can be shaped) but it may even be too shady for them. You might possibly be able to espalier a climbing hydrangea (Hydrangea anomala petiolaris, zone 5) there if the location is very sheltered, although it can take five years for this plant to become established and begin to grow well so it may be too slow. I would suggest you work with your local professional nursery staff to analyze the growing conditions where you want to do this and see what suggestions they may have toward meeting your design goal. Best of luck with your project!
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