Q. I reside in Bucks County, PA and would like to plant a privacy hedge around the perimeter of my rear yard.
Carpinus betulus, European Hornbeam, Common Hornbeam, withstands heavy pruning, is excellent for screens and hedges. Without pruning it will grow 40 to 60 feet. Slow growing, but choice, in ten years it will grow 10 feet unless ample moisture and fertilizer are provided. Performs best in full sun but will tolderate light to moderate shade.
Carpinus betulus 'Columnaris' is - columnar. C.b. 'Fastigiata' has dense, compact, close-knit growth and can develop into an oval shape rather than an upright one. C.b. 'Pinoccheo' is narrow and strong growing.
Carpinus caroliniana, American Hornbeam, also is a possibility for you to consider. It was reputed to not take pruning well, but new discoveries indicate it is readily prunable and will serve as a hedge.
A third choice would be Acer Campestre, Hedge Maple. Displays excellent tolerance to drought and heat, full sun or light shade, withstands severe pruning. A.c. Queen Elizabeth may not be perfectly hardy in Zone 5.
(You didn't specify your zone and I know Bucks County is north of Phila..) The trade name for A.c. Queen Elizabeth is Acer campestre 'Evelyn'.
These are all deciduous trees as is the privet, and offer more landscape interest than privet because of the density of the foliage. Privet is invasive and is not recommended. Much pruning for a 100 ' hedge will be required.
Would you be able to consider a flowering shrub as your hedge? I would suggest the Syringa (lilac) patula 'Miss Kim' , sometimes labeled S. palibiniana which does not really exist. S.p.'Miss Kim' is said to grow smaller than it actually does. 4' to 6' or 8' by 1 1/2 times as wide is more accurate. The other shrub type of lilac I would recommend is Syringa meyeri (4'-8' high and 1 and 1/2 times as wide. Sometimes labeled as S. meyeri is S. microphylla, Littleleaf Lilac), 6' by 9 to 12'. These lilacs would offer a free standing and fragrant hedge, also deciduous and much easier to maintain as they are not susceptible to powdery mildew and definitely should NOT be sheared. (This gardener has Syringa meyeri growing in shade with some early morning and late afternoon sun filtered from overhanging trees. Shrub is thriving.)
Let us know what you decide to plant.
These recommendations are from Michael A. Dirr's books here in the McLean Library at the Pennsylvania Horticultural Society where you are welcome to browse and do research even though you are not yet a member. Mr. Dirr is a noted authority on trees and shrubs. +