Inspect the base of the plant and the base of the main stems for suckers. Trim these thin, whip-like stems from the plant, using pruning shears to cut them flush with the soil or the main branch. Suckers grow more quickly than the rest of the oleander. They also flower poorly.
The evergreen oleander shrub produces dense branching and lush green foliage. These shrubs flower most heavily in spring, although some varieties continue to bloom through the summer months and sometimes into winter. Oleanders can reach up to 30 feet tall, depending on the variety. Proper pruning results in a much shorter plant. You can prune and train an oleander to a height as little as 3 feet, if desired. Prune the shrubs in early summer after the main flush of flowering passes.
Prune out one-third of the oldest stems from overgrown oleanders to begin trimming them to a shorter size. Remove these stems at their base.
The following year, cut out a third of the stems a second time. Trim back the remaining stems to one-half their height.
Trim the plant back by one-half its height again in the third year, so the remaining bush is at the desired size. Cutting back the plant gradually over a three-year period diminishes the chances of shocking and killing the oleander by over-pruning.
Maintain the size of the oleander with yearly pruning. Cut back the branches by up to one-third their height so the oleander remains short.
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