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.
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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.
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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.
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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.
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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.