While pruning a rosemary plant is not needed to keep a rosemary healthy, there are several reasons why a gardener might want to prune a rosemary bush. It may be that they want to shape the rosemary or reduce the size of the rosemary shrub or to create a more bushy and productive plant. Whatever your reasons for wanting to prune your rosemary, there are a few things you need to know about how to prune a rosemary bush.
When to Prune Rosemary
Rosemary pruning can be done anytime during the spring or summer up until four to six weeks before the first frost.
Pruning rosemary after this time, or in the fall and winter, can cause the rosemary shrub to focus on growing new, tender growth rather than hardening off and protecting the growth that it has. If a rosemary bush does not harden itself off, it will be more susceptible to winter damage which can kill it.
Tips for How to Prune a Rosemary Bush
Before you prune your rosemary bush, make sure that your pruning shears are sharp and clean. Blunt or dirty pruning shears can result in ragged cuts that can leave the rosemary plant vulnerable to bacteria and pests.
The next step in how to trim rosemary bushes is to decide why you want to trim the plant.
If you are trimming the rosemary to shape it, say as a hedge or a topiary, draw a mental picture of what you would like the plant to look like and trim away the branches that do not fall into that outline. If your shaping needs to remove more than one-third of any branch, you will need to prune the rosemary back in stages. You can prune back branches by one-quarter, but you will need to give them a season to recover before pruning again.
If you are looking to reduce the size, you can prune back the overall plant by one-third at a time. Then wait two to three months and you can prune back by one-third again.
If you are doing rosemary pruning simply to create a busier plant, you can remove the end one to two inches (2.5 to 5 cm.) of the branches. This will force the branch to split and will create a bushier plant. This technique is particularly helpful if you are growing rosemary for cooking, as this creates more foliage in a more compact space.
You may also find that your rosemary plant is in need of some rejuvenation. Find tips for this here: Rejuvenating Rosemary Plants.
The steps for how to prune a rosemary bush are simple but important. Knowing how to trim rosemary bushes properly will help you keep your rosemary happy and manageable.