Monday, September 24, 2007

Best Time to Prune Smokebush

(A recent photo I took of Cotinus coggygria 'Royal Purple')

I have a few smokebush that have gotten really leggy and unattractive. What is the best way and time of year to prune so that they appear more bushy and full?

Smokebush (Cotinus coggygria) is a favorite deciduous shrub of mine and certainly a fabulous plant for the city. With its rounded leaf, unusual bloom that resembled a cloud of smoke, and attractive fall color, this shrub is great in groupings or alone in full sun to part shade. However, I too can relate to how they can get leggy if they have been unkempt for a number of years. If this has occurred, then you can prune the shrub heavily and over a few years you can help the plant to regain a more attractive form. Before I go on, keep in mind that because Cotinus bloom on wood that is a couple years old, you may sacrifice blooms for a season or two. However, you will end up with a shrub that you are once again happy to look at in the landscape and in time the flowers will come back bigger and better than ever.

The best time to begin pruning your Cotinus is in spring before it pushes out new growth. Inspect your plant at its base and identify three to five strong stems that make up the main structure of the shrub. Prune those stems back to two or three feet above the ground. Space out your pruning cuts selectively so that you are pruning every other, or every third stem. This allows you to begin to shorten the shrub without it looking too lop-sided or beaten-up. At this time you can also cut out any weak growth from the base to promote new stems for that growing season. The branches that you have cut should push out new growth during next summer that is nice and full of foliage. The following year, revisit your Cotinus and target the next third or half of leggy stems. I would choose to cut those stems back hard as well, again, selectively, pruning them to any where from 18” to 3’ or 4’ above the ground. Depending on the size of the shrub you might be able to rejuvenate your Cotinus in two years. If it is very large it might take three or four years of selective pruning to get it back to a desired shape. Eventually you will have brought all of the major stems of your shrub back to similar heights and the new growth from all of those cuts will give you the full, foliage-rich Cotinus that you have been missing. Continue to mulch and irrigate your shrubs regularly to promote a healthy plant and you will see large plumes of that pink “smoke” flower again in two years time.

As far as Cotinus obovatus, commonly called smoketree, personal experience and some research here in the library confirms that the tree form of Cotinus does not require the same pruning regiment as smokebush.

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