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Worried your shrubs are dead? What to know before you cutback your plants this spring

Paul Cappiello Ph.D.

Paul Cappiello Ph.D.

Yew Dell Botanical Gardens Executive Director

I know this is getting to be a topic that won’t go away.

We had a crazy winter. Plants died. We know.

We need to move on, but how? If I measure the need for covering a particular topic by the number of emails in my inbox or voicemails on my office phone, I’d say there’s plenty of life left in this topic thread.

I think the best place to start is at the very beginning of the current predicament. You have dead plants. Ok, that’s a good place to start. But exactly what does that mean? Did you just lose the leaves? Did you have a few inches of stem dieback? Is the shrub dead to the ground? Did it kick the bucket, leaves, stems and roots? Before you start whacking away with the lopping shears, it’s best to figure out what you have to work with. Here’s what to know about cutting back your winter-damaged shrubs.

How to tell if your garden plants, shrubs are dead

Dead leaves are pretty easy. If the leaves are still hanging on the plant but are the color of a brown paper lunch bag, I hate to break the news to you but . . . they’re gone and not coming back. If your holly or laurel or boxwood leaves dropped off over the winter, whether they are green, yellow, brown or black, I think you probably already figured out that part on your own.

For stem/branch assessment, we’ve covered the thumbnail test in the last few editions of this column. You scratch the bark with your nail or a pocket knife and observe the color of the tissue below the bark. If it’s a bright green or greenish white, you’re probably in good shape. If it’s brown, that’s easy. And most often, if the color below the bark is greenish/brownish, it’s probably in the process of giving up.
 
The key with the bark scratch test is to work your way back from the tip toward the base of the plant. Most times, if you have partial dieback, you’ll find brown, followed by brown, followed by brown, and then followed by green. Usually, once you hit green, the branches will be green from that point down. Also, if your shrub has green near ground level, it’s a pretty good bet that the roots are probably OK as well.
 
If your shrub is brown below the bark all the way to the ground, that’s when you have a bit of a predicament. If your plant is small and/or young enough, you can pop it out of the ground with your trusty garden spade and inspect the roots. If you see nice white, fresh-looking roots, you’re probably in good shape. Pop it right back in the ground. If the roots are mushy, black or smell a bit like a mixture of vinegar and old socks, you probably have some significant root damage. In that case, save yourself the trouble of replanting and just toss it on the compost pile.

How do I know when to cutback my shrubs?

The next step is to consider what kind of shrub you have, and when it comes to cutback decisions there are really two options. Suckering shrubs such as forsythia and nandina will annually send up new shoots from the below-ground crown of the plant. Non-suckering shrubs such as cherry laurels and boxwoods generally don’t send up new growth from the crown of the plant — at least not normally.

The nice thing about suckering shrubs is that they are already programmed to recover quickly if cut back or killed back to the ground. So if you have a damaged nandina or another suckering shrub, the best course is to take the pruning saw or loppers and cut off all the stems about 4 inches above the ground. Most likely your suckering shrubs that suffered stem damage will have roots that survived and will send up new growth soon if they haven’t started already.

How do I know when to cutback my non-suckering shrubs?

Non-suckering shrubs offer a little bit more of a challenge. Depending on the plant in question, laurels, boxwoods, and rhododendrons all respond a little differently. Each type of plant will have a stem diameter above which it won’t want to put out new growth. Some respond faster than others. Some just don’t like to recover from cutbacks at all. But we can follow a few basic rules to get us, or more importantly, our plants, headed in the right direction.

First, determine how far your stems show damage. If it’s just a few inches of damage from the tip, you can do a simple trim and leave the plant to do its thing. On the other hand, if your plants are already showing new growth popping out of the main trunk just above the soil line, it’s likely that the rest of the stems are dead. If you see that kind of growth from the base, now’s the time to make the big cut just an inch or two above the new growth.

How can I tell if my boxwood is dead?

But if like so many of our damaged boxwoods you have branches that are killed back half way, that’s when it takes a little thinking. You want to cut back enough to remove the dead tissue. But at the same time, you don’t necessarily want to mow down the entire mass of the shrub if half of it is still alive. If that’s the case, first cut all the branches back until you just hit the live parts of each branch. Then, step back and take a look at the whole plant and continue to prune to shape it into something that makes sense. If most of the stems are 18 inches long and there’s one that’s live to 3 feet tall, the tall one may need to get knocked back a bit to make the whole plant look right.

And finally, a word on timing. As warm as our spring has been, most of what was damaged is now showing it’s brown color. You can go out there now, do your scratch tests and plan your pruning. But there’s no problem with waiting a few more weeks just to be sure.

This article was originally published in the Courier Journal on April 20, 2023.

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