This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
Little attention is commonly given to pruning or shortening in the branches of evergreen trees. Some of them naturally assume a handsome form, while others might be much improved by the operation. We do not refer to shearing into stiff geometrical figures, which are discordant to good taste, but to the thickening of the foliage without interfering with the graceful natural outline.
There are two common evergreens that bear free pruning, and may be worked into any desirable shape - the hemlock and the Norway spruce. Both of these trees, unlike most other evergreens and nearly all deciduous trees, grow well in the shade, and as a consequence, they grow well in their own shade - or in other words, the interior of the tree is not made bald by the shade of the exterior. The arbor vitas, on the other hand, suffers from shade, and the interior of the trees and of screens are found to be bare stems and branches.
No evergreen appears well when sheared smooth like a wall, although screens and hedges are often admired when thus treated. We much prefer the more free and rich appearance of an uneven surface out back with the knife. Such trees as the arbor vitae can be kept well filled with foliage only by an irregular cutting back.
Evergreen trees which tend to an irregular growth, like the hemlock, may, when planted as single trees, be greatly improved by shortening in any stragglers. We find it necessary to do something of this kind on nearly every tree. A nurseryman informs us that he has only to prune his hemlocks into shape, to sell them at any price. There is a vast difference between a thin straggler, and a rich, green, dense, tree, with a handsome even outline, and with a form sufficiently graceful to be free from all stiffness. - Country Gentleman.
 
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