Landscape Cornerstones – Caring For Shrubs and Hedges
Flowering shrubs are roughly of two types, those which should be pruned in the spring and those which should be pruned after blooming.
Shrubs like Mock orange, Tartarian Honeysuckle and Van Houttei Spirea bloom in the spring and they should not be pruned until after blooming. Later flowering shrubs such as Hydrangea should be spring pruned to shape up the plant and encourage new growth on which the bloom will appear. Dead and injured wood should be first cut out and the amount of trimming decided on afterward.
Old growth can be cut out at ground level and then new growth headed back to provide a rounded compact appearance. Shrubs such as Azalea, Deutzia, Smoke Bush and Weigelia should only be very lightly pruned, if at all. Bush clover, Buddleia, Spirea, Anthony Waterer or Spirea billardi and summer flowering Hydrangeas should be cut right back to the ground in the fall to prevent winter kill.
As with other plants, shrubs should be fertilized, and treated for insects and disease control regularly. Green Cross Shrub and Evergreen Dust is a handy, ready to use control for most common pests.
When new hedge plants are set out, they should be headed back quite severely in order to promote “Bushing Out” at the base. The sides of individual plants touching each other should also be cut back to promote interlocking growth.
Another point to bear in mind from the beginning is that the sides of the hedge should be wider at the bottom than at the top, so that the lower foliage can obtain adequate sunlight. This is especially important with evergreen hedges in order to prevent holes or gaps in the lower part of the hedge later on.
Where informal hedges are being grown, one clipping in early spring is often sufficient except with fast growing hedges such as Chinese elm.
With formal hedges, the first trimming should be done in late spring or early summer, this being to shape the hedge up. This should be followed by a second trimming about one month later, or when there is 1-2 inches of new growth showing. It might be noted that summer clipping tends to check growth and may weaken plants whereas dormant pruning favors wood production.
Practice summer trimming only on healthy, vigorously growing hedges.
Evergreens tend to start spring growth a little later than deciduous plants and so should not be trimmed as early. Cedar hedges may be trimmed in September after growth has ceased thus they require but one clipping per year.
When trimming hedges, clippers should be sharp so that young shoots are cut cleanly and not bruised. Cutting the sides first allows top clippings to fall clearly to the ground.
An annual spring dose of fertilizer together with underground sprinklers will aid greatly in maintaining a healthy, vigorous hedge. As hedge plants tend to compete with each other for moisture it is important that the hedge be well watered, during dry periods. Evergreen hedges should never be allowed to go into the winter season with the soil in a dry condition otherwise severe windburn and winter-kill may result.
Hedges of privet are often killed back to ground level by the winter in many parts of Canada but they usually re-grow in a satisfactory manner if the dead wood is removed. Some varieties of privet are very sensitive to some insecticides, so, check with your local nursery or garden center before applying any chemical. If used on the sensitive varieties, the leaves may be severely injured and drop off the plants.
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