Pruning can take on many names and be performed for many reasons, utilizing a myriad of techniques and tools. Most people are familiar with hedging or shearing.
Shearing is used to create a neat shape or formal look and to create a dense branching habit. Shearing slows the pace at which a plant increases in volume. It does not decrease the amount of growth a plant will produce in a season; it just spreads the growth over more growing points. Shearing can be used to create Topiary and Standards. A Standard is a plant trained on a single stem to form a head, often done to Hydrangeas and Roses.
Thinning is less familiar to many but is very important to plant health and its lasting beauty. If we want to keep our plants compact, we need to allow them to produce leaves on internal and external branches. When a plant is very dense, the interior is dark and does not support green growth. A healthy plant needs many leaves to collect energy and create stores of energy needed to flower. Thinning allows sunlight to penetrate into the plant encouraging inside growth. This allows for more leaf mass to be maintained in a smaller space. Thinning does reduce the number of growing points and thus accelerates the growth rate. This is useful in expediting the growth of specimen plants and increasing the height of Rhododendrons planted for privacy purposes. For hedges, the thinning and shearing process is simultaneous.
Selective pruning for structure can help us achieve many varied results depending on our needs and constraints. Pruning can be used to create a look such as, Oriental Style, Formal Box Hedges, Topiary, Naturalized, etc. Pruning can accelerate or slow down the increase in volume of a plant. We can make a plant more open and show off its structure or bark to allow some light in or an outward view. We can make plants denser to reduce noise, dust, light, or sight allowed through. Some plants are at their best when the twigs are young such as Red Twigged Dogwood or Pussy Willows. Some yards need an espaliered hedge due to space constraints. All of the above can be achieved with proper pruning techniques.
Flowering is absolutely affected by pruning. In the wrong hands a pair of pruning shears can stop a Hydrangea, Rose, Wisteria, Clematis, Kerria, Lilac, Dogwood, etc. from blooming each year. It is important that the person pruning knows which plant they are pruning and where and when they flower. Most plants are more apt to flower on branches that are growing horizontally vs. upright growth. Flowering trees will be more attractive if they are allowed to flower in all areas of the tree and not just the periphery.
Removing dead and diseased branches or branches that contribute to poor structure can drastically increase the joy and serenity we reap from the landscape. Plants that flower freely do not require cabling. They also require fewer pesticides and have a robust appearance. Regular maintenance by a qualified, caring, horticulturist is also much more cost effective to the growth of your investment. Ignoring problems and allowing plants to be continuously sheared into poor health actually diminishes the value of your investment.