Sunday, April 16, 2017

pruning rosemary

I've heard comment from others that the best way to prune rosemary is to never prune it. I don't agree. I think that rosemary when left alone, grows so vigorously, that it flops out, and becomes woody, then large branches die, leaving a scraggly mess. If you doubt this, see if you can remember the large scale rosemary plantings at the Century 24 movie theater here in Albuquerque. This past year, they had to remove a large number of half-dead/mostly-dead plants and then they pruned back the rest. Those that were pruned back look so much better this year.

But I do agree that shearing the plants several times a year into gumdrops as they do in many other public areas (i.e. gas stations) is equally ugly. So then what to do? There are a couple things to keep in mind. First, is that rosemary grows natively in an area populated with browsing animals, particularly goats. Although the strong smell from resinous oils keeps the deer and the rabbits away, it doesn't necessarily keep the goats away. Then, notice that rosemary blooms in late winter and grows strongly in the spring, then continues somewhat more slowly in the summer and slows down in the fall. Then also notice that rosemary blooms on old wood, that is, the growth that was made the previous year (this also explains why a young rosemary plant may not bloom very much). One more thing to think about is that if you want your rosemary to bloom in those glorious clouds of blue that I love. If you just want rosemary to use as an herb, you might want it to grow as many tender new leaves as you can (although I can't imagine anyone wanting that much rosemary!).

So given that rosemary grows fast and is native to an area with browsing animals, I think it is okay to prune rosemary hard. That being said, don't prune rosemary to where there are no green leaves, because it won't sprout new growths from that old wood. Personally, I think it is okay to shear rosemary into mound or gumdrop (!), then pick prune for shape, and to remove old dead wood, and the scraggly growths and to remove the clumps of stems at the ends of branches that results from shearing the shrub a few times. It takes some time. You can also shear rosemary into a hedge as they often do in California. But I think the most important thing to remember is when to prune rosemary.

I pruned one of my 'Gorizia' rosemary late last fall because I was too busy to prune it in the spring and it began to cover my window. The unnamed rosemary next to it, I left unpruned since I was frankly too busy, and it didn't cover a window. This spring showed me the results.

'Gorizia' grew new leaves strongly this spring, but produced almost no flowers, since I had pruned off all the growth from last year, which would have been the flowering stems.

The unnamed rosemary, was covered in blue flowers this year. Now that it is done blooming, I have pruned it back, but this means that I have pruned off all the lush new growth that is produced on the ends of the stems as the plants finishes blooming. 'Gorizia', having no blooms, started growing new leaves much earlier.

So when to prune? If you want flowers in the spring, prune right after blooming, so that it will produce a lot of new growths that will bloom next year. If you don't want flowers or if you just want early tender growth, prune in the fall or winter.

And how to prune? If you want flowers, prune hard so that the plant produces a lot of new growth which will bloom all along those year-old stems. Also prune hard if you want long straight stems for barbecue skewers. I guess that means that my opinion is to prune hard. BUT, only prune ONCE a year if you want flowers. If you want a gumdrop (no!) or a hedge, you will need to shear it several times a summer. Although it may seem contradictory that I prune into a gumdrop but then I hate gumdrops, when I prune once a year, it quickly outgrows that gumdrop appearance. It also looks less like a gumdrop since I prune out the witches brooms that grow after shearing to the same spot a couple of years. 


  1. Thanks, this post is just what I needed! The 'Arp' I pruned hard last year grew vigorously and is now blooming profusely. I'll prune hard again when it's finished blooming.

  2. Great post and reasons about why to prune, from the natural world to the different aesthetics people want. I forgot about the "never prune" crowd your area has...they are usually the "who needs design?" crowd, too!

    I never thought to prune hard as you stated, but so true. I was always afraid to prune after October, in case it induced tender new growth, but maybe that's not an issue.

    1. In my experience, if you prune once the weather is cold, it won't stimulate growth. If you prune in the middle of fall, it might grow new growth just in time to be hit by the cold.