Q. I have a rosemary bush in the front yard that's very healthy but has grown quite big in the seven years since it was planted. Is there a technique to trimming? I tried once before and it looked like a really bad haircut.
|Rosemary with a bad haircut from overzealous hedge shears|
A. Any older, woody plant will have its leafy growth on the perimeter of its canopy. If the plant canopy is dense, which is typical of rosemary, all of the leafy growth will be in a 2 inch layer along the outside of its canopy.
Leafy growth needs sunlight. Shade causes leaf drop and prevents leaves from developing. Dense plant canopies don’t allow sunlight to the interior. This means that the woody growth in the interior will be leafless, bare, naked. If you begin cutting away deeper than 2 inches then you will expose the interior, bare wood. This does look like a bad haircut.
The good thing is that bad haircuts are not permanent. New growth emerges from these bad haircut areas because of sunlight and the stimulation the plant receives when it is pruned.
|Rosemary pruned around the tree|
Shaping plants should begin when they are young. You cannot wait until they are several years old to begin shaping them unless you are willing for that plant to have a bad haircut for a while.
Pruning rosemary depends whether you want it as an ornamental or you plan to harvest the rosemary for cooking. If you are harvesting rosemary for cooking you want to harvest soft succulent growth.
Alternatively you can harvest the woody growth and strip the leaves off. Commercially pruning is done with a shears because it is faster. Again, if you cut too deeply with a shears it will look like a bad haircut.
After pruning always make sure there is enough warm weather for regrowth to occur. Water and fertilize the plant to stimulate new growth and recover from pruning.
If you want your rosemary to be an ornamental, it can adhere to any shape you want to give it. It can be sheared or it can be pruned with a hand pruners. During this last holiday season we saw upright rosemary pruned into small Christmas trees available at nurseries and garden centers. Just don’t cut the plant too deeply.
|Rosemary pruned more formally like bangs in a haircut|
I prefer a more normal look. This is done by reaching deep inside the plant and removing older wood with a hand shears. By reaching inside to make cuts they are hidden by the remaining growth. If you prune like this, it will never look like the plant was pruned; just smaller.
|Rosemary pruned informally|
Look for the longest growth, follow the stem back inside the canopy to a place where it joins another branch. Cut and remove the longer stem and leave the shorter one. This would be done in several places each year to keep it restrained.