Every bush has a characteristic shape and size, and for each there is a best pruning technique to bring out the maximum beauty of its flowers, branch color and structure. Some require little pruning; others more. For the best pruning results, identify all your bushes and learn about their unique attributes. Bushes vary widely by region, so the most reliable way to identify the ones you don't recognize is to take a clipping to a nursery. Usually the nursery will have reference books with a photo of the characteristic shape and can tell you the mature size, as well as special pruning instructions. Keep the key information on a rough sketch of your yard. Tip: You can prune almost everything in early spring. Just be sure to get to it!
Some arborists call these the 4 Ds. Start with the dead and damaged branches, because they make the plant look bad, and encourage rot and disease. Also cut out wilted, dried or diseased branches as soon as you spot them, to remove the disease before it spreads. “Deranged” includes a broad range of branches that cross (the rubbing wears away the bark), loop down to the ground or simply look out of character with the bush (stick out at an odd angle or grow alongside the trunk). This pruning also thins out the bush, opening its interior to more light and air, which encourages fuller, healthier growth.
Cane-type bushes, such as forsythia and hydrangea, usually send up new canes from their roots every year. In general, prune out the oldest (larger) wood to control the bush height. It's also OK to trim out newer canes to thin the interior of the plant and let in light as well as to control its spread. If one of these bushes has gotten too big and out of control, you can often cut off all the canes and the roots will send up new shoots. You'll have a nice new bush in a year or two. Note: All bush categories have exceptions to these rules. So know your plants!
This “heading off” technique channels more growth energy to smaller side branches, which will then fill in vacant areas. Make this cut at a side branch or 1/4 in. beyond a bud. Be selective and watch the results from the previous year to help gauge future growth. It works best on bushes and trees that grow mostly from one or a few stalks, as opposed to bushes that continually send up new shoots (suckers), like lilacs and forsythia.
It's tempting to grab the hedge shears and shape a bush by cutting off the branch tips. This “flattop haircut” approach may look fine for a year or two, but it stimulates growth on the outermost branches, forces the bush to grow into an unnatural shape (your idea rather than the plant's) and fails to control size. The bush actually grows larger and becomes more difficult to bring back to size without being ruined. The exception is hedge-type bushes.
If neglected, many bushes get too big and dense. While the foliage might look OK this year, next year it just might be too big to prune back without butchering it. Instead, it's better to control size and shape by selectively pruning out a few entire branches each year. Cut them at a larger branch or the trunk. This also opens the plant to light and encourages healthy growth from the interior.
Unlike cane-type bushes, evergreens and other “nonsucker– type” grow from their existing stems. They develop a more permanent branch framework and usually need less pruning. If your landscaping was well planned, these bushes, especially evergreens, will grow to fit their spot with relatively little help. They'll need only a light annual pruning to remove dead branches and to control size and shape.
The branch collar is the bark swell that encircles the branch. If left intact, this collar will soon grow over and cover the wound. Don't leave stubs. They'll rot and might become diseased.