Anybody can shear plants, but not everybody can prune plants properly. Black and Decker, Stihl, Echo and other manufacturers of hedge clippers have caused many landscapes to look alike. Foundation plantings are shaped into cones, balls, cylinders or squares. Sheared plants lose their identity and begin to look alike regardless of species.
Pruning, on the other hand, helps plants exhibit their most desirable attributes. Spring-flowering plants like forsythia, weigela, spirea, viburnums and strawberry bush and summer-flowering plants such as roses, crape myrtle and hibiscus benefit from proper pruning.
Properly pruned forsythia, spirea and weigela should resemble fountains when in bloom. This characteristic can only be achieved by selectively removing the older stems near the ground and allowing only strong, healthy brownish-green stems to grow and arch. When pruned immediately after petals have fallen, the new stems will be covered with large flower buds that will burst open next spring. Properly pruned, these plants will develop stems four to six feet long in one growing season. They will need tending only once during the year. If you are shearing, you must do so almost monthly, if not more often.
With regards to viburnums and strawberry bush, you need only to prune out crossing branches and branches that are detracting from the appearance of the plant. Shearing these species removes most of the flowers.
Woody species that are adapted to shearing include azaleas, camellias, fir, hollies, junipers, pine, privet and yews. When shearing, shape the plant so it is narrower at the top and broader at the bottom. When the top of the plant is broader than the bottom, the bottom leaves are shaded out, leaving the lower part of the plant bare.
Allow an inch or more of current seasonal growth to remain on the plant. Shearing away all new growth, especially on older plants, results in individual small branches turning brown and dying.
Do not shear azaleas or camellias after mid-July. Flower bud initiation for these species begins in mid-August, so shearing in late July and August will result in fewer flowers the following spring. Flower bud initiation occurs only on young, vigorous-growing new shoots.
Heavily shearing junipers often results in plants becoming infested with spider mites. To avoid this problem, shear only once a year. Most species of junipers will generate two flushes of growth each year. The first flush generally ends in late June, and the second generally does not begin until mid-July. Delay shearing until the beginning of the second flush of growth.
Soon after you notice new light-colored growth at the ends of the branches, begin shearing. This will allow the plant to develop a feathery appearance and will minimize conditions favorable for spider mites.
Do not shear pine or spruce until the needles of the new growth are at least half the length of mature needles. Shearing these species too early will result in breaking many of the new branches.
When pruning and cutting roses, pay attention to leaf patterns. The leaves on roses have either three or five leaflets. If you examine the stem, you will notice that the leaves just below the flower buds have only three leaflets followed by several leaves with five leaflets. To promote the development of strong stems, always cut the stem above the bottom five-leaflet leaf. The vegetative bud in the axis of the five-leaflet leaf is always larger than the vegetative bud in the axis of the three-leaflet leaf, resulting in stronger and longer stems.
Never prune or shear boxwood plants. The disease that causes boxwood decline is easily spread from plant to plant on the blade of pruning shears and hedge clippers. Boxwoods are best pruned by breaking stems on a cold winter day.
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