Should I Rejuvenate My Shrubs? Do I Dare?

Additionally, as shrubs age, flowers can become less and less abundant. Often, fresh new growth is necessary for the best show of blooms. And since pruning stimulates new growth, your flowers will be more productive. But be aware this fresh new flowering may take a full year to develop. We’ll cover that in more detail later.

Also, many shrubs are grown for their vibrant leaf colors. Like flowering, the new growth will set the stage for excellent color ranges on your leaves in the spring, summer, and fall.

Hello, by the way! I’m Kevin, and I’ve been pruning professionally and as a hobby gardener for over 30 years. In the early years, fresh out of college, I had a lot of book knowledge but no real practical experience on shrub pruning.

I’ll be honest: I think I scared a few of my early customers to death when I began to prune. I was a little nervous myself in those early days. I remember cutting back some 10-12 foot Ninebark shrubs down to 12 inches. They had probably not been touched for 10 years!

My bedside manner is better now, and I forewarn my customers about what to expect.

Examples of What Rejuvenated Shrubs Look Like

Here’s an example of a group of Summer Wine Ninebarks after rejuvenation. I planted them close to create a screen around this wellhead. I let them blend, but eventually, they build up dead wood, and I rejuvenate.

This last photo is in the second year:

Here’s what I’ve learned:

• Make sure your shrub is in a healthy state with average soil moisture and nutrients. Shrubs that look nearly dead already will likely respond slowly or not at all. Plants have a lifespan, too. But it’s worth a try; you never know how a plant will respond.
• Only do rejuvenation pruning when the plant is dormant. In the northern Great Plains, Zone 4, I prefer late winter into early spring (March and April).
• Take into consideration the importance of flowers each season. Certain varieties need a full year for their flower buds to develop, so you may skip a year when removing all growth by rejuvenation.
• Be patient. Shrubs can be slow out of the gate in the spring after this hard pruning. But as soon as the summer heat arrives, they will “take off.” Consider adding some fertilizer around the base of your shrub. I like to use Osmocote, an excellent slow-release pellet fertilizer.

I often find myself in situations where customers ask me to remove a shrubs because they have become too large or overgrown. It’s easy to convince them of rejuvenation at that point since there is nothing to lose; they’re already ok with losing it. However, over all these years, results have been very favorable, at least 95% of the time.

Another Example with Photos

Here’s an example of a Bloomerang Lilac pruned back hard in late winter and the growth stages throughout the season.

Again, this last photo is in the second year:

How often should I rejuvenate? Every year?

I recommend doing it every 3-5 years. However, I have an Amber Jubilee Ninebark that I have been cutting back hard every spring for over ten years. I planted it in a tight location, knowing it could easily reach 10 feet, but I wanted to keep it around 3-4 feet each season. The rejuvenation encourages new growth and excellent leaf colors that change throughout the season. So, annual rejuvenation can be done, depending on the variety.

Here’s a video that shows you the pruning and leaf colors on Amber Jubilee:

As I mentioned, ample water and nutrients are essential. Many of a plant’s food reserves are in the stems you remove, so the more frequent the “hard” pruning, the more you stress your plant. Ninebarks happen to be tough! So are Spirea shrubs if you are looking for another example.

Here is a look at Double Play Gold Big Bang Spirea in the same season:

What about the flowering you mentioned?

There are two broad categories when discussing flowering on shrubs.

• Does it bloom on new wood? or
• Does it bloom on old wood?

Flowering on new wood occurs that same season. New growth begins, and flower buds develop and bloom. Spirea and Potentilla shrubs are good examples of shrubs blooming on new wood.

Old wood is growth that needs a whole year to set flower buds. Growth emerges in the spring, flower buds develop throughout the season, winter comes along, spring comes along, and then flowering occurs that second season.

In short, it’s a matter of how quickly a plant sets flower buds and matures on the new growth. With the power of internet searches now, you can quickly find the answer to this flowering question on nearly every shrub variety you consider pruning.

Ninebark and Lilac shrubs are good examples of shrubs that bloom on old wood. The Bloomerang Lilac we showed previously is an exception and sets flower buds on new and old wood. I think it is worth the wait to skip a year of blooms on “old wood” shrubs due to how many more flowers you get on the newly stimulated growth.

Like the Bloomerang, there are also Hydrangea varieties that will bloom on both categories of wood.

Here are some photos of a rejuvenated Little Lamb Hydrangea and the growth stages that same season:

Healthy, rejuvenated shrubs can grow quickly! They can often attain nearly the same size that season because of their established root system.

So why rejuvenate if the shrub is back to the same size so quickly?

The difference will be in the appearance. The new growth will look more natural and flowing. Fresh. And less rugged, gnarly, or leggy. That new growth is perfect for gentle pruning (tip pruning or light shearing). It will also be easier to perform thinning cuts, keeping the shrub’s natural shape.

I’ve rejuvenated my shrub. It came back great! What do I do for 3-5 years until the next rejuvenation cycle?

How you treat your shrub after rejuvenation comes down to how close your shrubs have been planted together and how close they are to buildings or traffic areas.

If your shrub has been given the proper space listed on the label according to its mature size, you can leave it alone for many years and let it develop into its natural form. You may be able to leave your shrub alone for three years, five years, or more before you have to consider rejuvenating again; it will depend on the spacing and the desired look you are after.

If your shrubs look too crowded or large for your taste, you may have to do light pruning each season to keep them in check.

Rejuvenation Pruning Schedule

Using Summer Wine Ninebark as our example, the routine can go like this:

Spring growth has flushed out nicely after rejuvenation with several feet of new stems and foliage, but it already looks too big.

Late June into late July (in my area) is an excellent time to do a light shearing of 12-18”, usually in a globe shape for this shrub. A small amount of new growth will occur after this shearing, but not much. Remember, for this variety, you are removing some flower buds for next year, but not all, since you are only taking off 12-18”. And any new growth that develops after shearing will also start setting flower buds.

Or, if you prefer the shrub’s natural shape but still want to keep it smaller, do thinning cuts. Remove the longest canes, about two feet in, throughout the shrub, shooting for about 20% removal. With this method, your flowering will be better than a complete shearing the following season, as you leave most of the tip growth to set flower buds.

When the next season comes around, allow the plant to flush out its new growth and perform your shearing or thinning again mid-season. You could also do a light shearing and thinning in March or April each year.

Each year, repeat this cycle until dead wood starts building up or it starts looking leggy.

On Over-Planting

It’s crucial to re-mention the importance of giving plants the room they need to develop. Pay attention to the mature size on the plant label when planting. It will make all the difference in future maintenance and how you prune your shrubs.

Don’t feel bad if you have over-planted; I still do it all the time! My problem is that I love plants so much and want one of everything!

I’ll encourage you to check out this video, where I’ve highlighted over a dozen varieties of shrubs with before and after photos and a discussion on each, from rejuvenation pruning:

You can also visit gardenhike.com and view a blog post with still photos of all the shrubs covered in the video.

And I invite you to visit my Garden Hike YouTube channel for hundreds of other additional videos on northern gardening topics.

It’s March at the time of this writing, and for some reason, I have a Cardinal Dogwood on my mind, which is at the end of its five-year cycle—time to get at it.

Thanks for your time!

I hope this blog post finds you in good health!

Happy pruning!

Kevin

Photos courtesy Kevin Hollatz, GardenHike.com – used with permission