Cotinus Care in Yonkers

Question:
Oh please tell me that it is still OK for me to prune "my baby" which is really starting to make me very worried. It is more like a tree than a bush/shrub and I've let it grow to high and I did not prune it hard by March 31. I did prune back the long branches but the base of the "shrub" is more like a tree shape having a right and left side with the middle having been destroyed in a hurricane two years ago. This year, only the left side is beginning to leaf with the right side still bare but amazingly, growth pushing up from the bottom. The leafless right side is alive - how do it know? - if I prune off a small branch, the smell is there and if you scrape the bark, you see green. I would estimate it's overall, crooked height to be about 5' tall.

So, after having read your article and only having about 10% of the shrub/tree in leaf, my question is:

Can I safely prune back now/today to approx 3' tall, fertilize and keep moist, and hope that it will begin to leaf more evenly?

This is the Queen of my Garden and I must save it and restore it to its overall beauty. I don't care if it flowers; I just want all the leaves to return all over the plant and enjoy them as they sway in the breeze and look like silver when it rains.

thanks for your help; it is greatly appreciated.

I asked if she could send me some photos to get a better idea of the situation and here is one:She also added:
Incidentally, I lost my first one. Following its demise, I sent a soil sample to Cornell in Illinois (I think) because I suspected verticillium wilt and I know this shrub does not do well under these conditions. I hope this one is not falling prey to the same fungus.

To date, I have fed it with Plant Tone but if there is something else that I should use to strengthen it, please let me know.

To all this I answered:
The left side I doubt is going to come back. There might be some green left in the tissue but it is not going to come back nearly as well as it once was, if at all. Cut the left side back to the ground and remove that dead stalk entirely. I also see that there is a stub in the middle which looks like it stands about 4”-5” tall with no growth. Cut that back to the ground as well. Since you are getting all that new growth from the bottom you might as well capitalize on that, even if it is not the ideal situation. It means in the long run the shape of your Cotinus will be quite different than the tree form it was, but it will certainly survive, and that’s the important thing. Cutting back that dead wood on the left side and in the center will continue to push out new growth from the base and you will end up with more of a shrub form. Ideally I would suggest cutting the right side stalk back all the way to the ground too, but since right now that stem has most of the plant’s foliage on it, I’m going to say hold off on that for now. In order for the Cotinus to have the best chance of survival, I am sorry to say it might look a little funny for this season, but with proper, spaced-out pruning it can still be a beautiful presence in your garden. On the right side I would remove any shoots that have no growth on them, of which I see a couple in the photograph. Prune them back to the next branch or trunk where there is healthy growth and foliage. While the shrub pushed out new growth from the bottom and establishes new leaf and stem tissue you want to remove as little living tissue as possible. As a general rule of thumb, you can always remove dead wood from a tree or shrub, but you want to allow the healthy parts of the plant to come out of dormancy and grow with as little stress as possible, especially early in the season. So, you will be left with a bunch of growth from the base and the “odd ball” stalk on the right side. Like I said, it will look funny, but if you remove the right side now the shrub might suffer too much stress. Therefore, I would remove the right stalk back to the ground, like the left and center pieces, but not until next winter. Next spring your Cotinus will then be a shrub form with new growth flushing out from all sides and you can prune it lightly to give it a better shape.


Regarding the fertilizer and verticillium wilt:
Do not go crazy fertilizing your shrub right now. If you have applied some Plant Tone to your garden this spring that is fine, but when it comes to perennials and shrubs, your plants are going to be happier if you don’t overdo it. Annuals and tropicals and turf can be “heavy feeders” as we call them, but over-fertilizing perennials and woody plants can force them to produce more stems and leaves than they want to and that can lead to unnecessary stress. Once established in the landscape shrubs have their own agenda and know their abilities and limitations based on the conditions they are living in, and often we should live with that instead of over-compensating to force what is not natural. Especially as a plant gets older it adjust to the nutrients in the soil and often does not want too much extra coddling. Also, regarding diseases, always be sure that you are taking care of the cultural needs of the plant before jumping to conclusions about dieback being the effect of a certain disease. Because a plant can be susceptible to a certain disease does not mean that that is your answer. I have been working closely with Cotinus for easily 10 years now and I can comfortably say that I have never seen one die because of Verticillium Wilt. Often irregular watering, soil that doesn’t drain properly, or being situated in an area without enough sun, those are often the culprits. If you do suspect a disease is present, be sure to familiarize yourself will all of the symptoms so that you can diagnose with the greatest degree of certainty. And either way, remember that proper plant care is always the best solution, disease or not.

Cotinus, Hibiscus, and "Rejuvenation Cuts"

(an image of Cotinus coggygria 'Royal Purple' taken last summer, photo credit: Alex Feleppa)

Question:

I have 5 purple smoke bushes, two Rose O’ Sharon hibiscus and three Luna hibiscus. A friend advised me to prune them all to the ground in late winter/early spring in order to get them to branch out. So in late February, that’s what I did. I cut them all to the ground. Now it’s March 31st and there are a number of other shrubs in my yard (snowball, honeysuckle, hydrangea, kerria) that are leafing out, but there are NO signs of growth in my smoke bushes or hibiscus. Did I probably kill them?

Answer:

Thanks for writing. Honestly, I doubt you killed any of those shrubs, especially because all three of those are some very tough plants. However, by pruning them back as heavily as you did you cannot expect them to grow and act quite the same way as they have in years past when you did nothing to them.

Allow me to give you a little botany/horticulture refresher. In the fall the shrubs have built up their reserves of energy, in the form of carbohydrates, and they store that energy so it can be used to help the shrub properly leaf out in spring. Deciduous shrubs leafing out requires the majority of that finite amount of stored energy, and once the new leaves are out, the shrub can begin a new year of photosynthesizing and rebuilding those reserves. Now, this is not to say that “rejuvenation cuts”, as I learned to phrase them, are a bad idea. Like you said, they promote new growth from the base and often can help you achieve a more full and bushy looking shrub. However, you do want to think about the fact that your shrubs now have to do “double duty” because of those cuts in relation to a finite supply of energy. What I mean by “double duty” is first the shrubs have to callus those cuts, then they have to push out new growth.

The cells right where you cut are going to callus in order to prevent insects and disease from infiltrating the stem and root tissue. This, of course, requires energy. Right below the bark on all woody plants is the cambium, the layer of xylem and phloem that carries water and nutrients vertically throughout the shrub. Because the shrubs are determined to stay alive, the cambium will force “dormant buds” right below those callused cuts to swell, leaf out, and grow into new shoots. We hope that the new shoots will grow large and healthy and provide you with a great new look in your garden. However, I hope my description has helped to clarify why that will take a lot longer than in years past when pre-formed buds simply had to leaf out with an energy supply they knew was not being used anywhere else.

For your own education, in the future this is what I would recommend. I would have advised you to make some rejuvenation cuts, but I might have recommended taking back half of the stems instead of the entire shrub. The following spring the dormant buds and new growth emerge from where you have pruned, but the shrub also has some older branches and buds in place to ease it through that stress. Then next winter you go back again and, assuming the first cuts led to new growth like you wanted, then you cut back the other half of your older branches. The process is elongated over two seasons, but by the second spring you have a shrub significantly less in size that you know will bounce back well and not die on you because of too much stress.

Now, again, I do not think you killed your shrubs. But, I do think that because of the need to callus and then leaf out your shrubs are going to be a bit behind the rest of your garden. For my gardens here in New York, Cotinus (smokebush) and hardy Hibiscus tend to leaf out and flower later in the summer than many other shrubs so I might guess it will be another month before you see much new growth. Another important thing to know now is that you want to provide proper care and not add additional stress to the situation right now. Keep the shrubs well watered, mulch them but do not bury the crowns of the plant where the buds are trying to emerge, and keep an eye out for potential pest issues. You do not need to fertilize or apply any extra nutrients, just let the shrubs bounce back as best they can on their own.

Best Time to Prune Smokebush

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

Question:
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?

Answer:
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.