Real Talk: Cutbacks

For many, the thought of eliminating an invasive plant simply by cutting it back—without the hassle of heavy labor or herbicide exposure—sounds like a dream come true. Just keep trimming it, and the problem disappears? Sign me up! But does this method actually work? Let's dive in!

Real Talk - Does cutting back a plant over and over again kill it without having to break your back or use herbicides?
 
One of the strategies recommended to kill invasive plant species is to routinely cut back the unwanted plant to the ground till it dies. By many folks, this is considered a better method because you a) don’t need to apply a systemic herbicide which can have a long half-life in the environment and expose yourself and wildlife to potentially harmful side effects and b) is less backbreaking and labor intensive than digging the plant out manually.
 
For many, the idea that cutting back an invasive plant can kill it without dealing with the labor or the potential herbicide exposure is a godsend. All I gotta do is keep clippin’ that bad boy and my problems go away? Hallelujah. But does it actually work?
 
Let’s get into it.

The Premise
 
You see an ominous stand of some terrible plant in a client’s landscape. Think: running bamboo, Canada goldenrod, bull thistle, Japanese stiltgrass, English ivy, barberry, Himalayan berry, or Japanese knotweed. You give a mighty sigh and raise your eyes to the heavens above. “How am I going to get rid of this headache before I try to install a native plant landscape,” you think. You heard about a cutback method where you identify the plant and cut it down to the ground. By cutting the plant all the way to the ground, you are removing its ability to photosynthesize and essentially running the clock on the root’s stored carbohydrates until the plant eventually withers and dies. One person can cut things back over and over again - it’s a lot easier than trying to wrangle up the labor to dig everything out, lock, stock, and barrel. Plus, you were hoping to walk lightly on the land, avoid disturbing the soil, and waking up the seedbank (with who knows what horrors lurking below). Cutting back also sidesteps the potential issues around herbicide application. You think, what a deal. Let’s do it.
 
But here’s the thing. Every method has its advantages and disadvantages. It’s important to consider the potential problems and if they apply to your situation before you choose to embark on that path.
 
But do cutbacks work?
 
In a word, yes.
 
But it’s a yes with an asterisk. And the asterisk is doing a lot of heavy lifting.
 
Whether a system works or doesn’t work depends less on the theoretics surrounding the practice and more on the commitment and consistency to see the system through. In our experience, the cut back method to remove invasives falls into this category. Here are some issues we’ve experienced when employing the cutback system:

The Hang-Ups
 

1. The plant has A LOT of stored energy - we’re talking about monster tubers here. Japanese knotweed, non-native cattails, and even native pokeweed are a huge headache because they store so much energy in their roots that it will take a long time to deplete the energy stores just by cutting back. That means you’re going to be returning to routinely cut back for quite some time. If you’re down with that, proceed
2. The plant has many, many roots - some plants send out extensive, winding root systems and only need ¼ of an inch left of broken root to be alive in the soil for it to return (i.e. bindweed or ground elder). You can cut it back, but a new shoot will emerge anywhere along its extensive root system, kind of like an invasive weed version of whack-a-mole. If you’re committed to hunting down each emerging shoot, proceed.
3. The plant has many, many seeds - one of the ‘delights’ of aggressive invasive species and why they’re so successful is that they have more than one means of reproduction and they’re really adaptable. Most of the time, it’s not just spreading roots that’s the issue - it also produces a plethora of seeds that can remain viable in the soil for 10 or more years. This is the case with Japanese stiltgrass. For plants with a ton of seeds, it helps to do a one-two punch of cutting back invasive material all the way to the ground and then immediately smothering it with plastic and solarizing the site or piling on wet cardboard to block sunlight and air from reaching the seed. Then you have to be careful not to disturb those lower soil levels later, so you don’t awaken the monsters beneath. If you’ve got the resources to cut back then immediately smother, proceed.
4. The ability to cut back as often as the plant returns isn’t feasible - And here’s the real fly in the ointment. To deplete the plant’s energy stores, you need to starve it of photosynthetic energy. Every time the plant returns and grows long enough to rebuild root energy stores, the closer it moves you back to square one. If you are already maxed for time and have a to-do list a mile long, returning to a site over and over again to cut back invasive weeds just as they’re emerging may not be the most pressing thing on your agenda. A way to sidestep this issue is to smother the site after a cutback (cook the plants with plastic in a sunny site or rot them thoroughly with wet cardboard and mulch in a shady one). For a large-scale site, however, smothering may not be feasible. Additionally, clients may not want to look at a bunch of plastic or cardboard/mulch while you and the maintenance team are periodically checking to see if the invasives are well and truly dead before planting with natives. If this is the problem you and your team are facing, it may mean that cutting back invasive plants as a method of removing them isn’t the pathway for you. If you’ve got the ability to return to the site consistently until the plant disappears, proceed.

The North Creek Experience
 
Earlier, we mentioned Canada goldenrod (Solidago canadensis) as a headache. Yes, this is a native plant to our region. Yes, some folks would be delighted to have this autumn beauty gracing their landscape. However, our fiendish patch of Canada goldenrod wants to rule the world and is in one of our bioswales where we have been trying to encourage other native goldenrod species for the last 10 years. Each early summer and each fall, our plant department dutifully marches out and cuts the Canada goldenrod to the ground. And each spring and again in late summer, the plant returns. The plant is not gone. Not after the years of cutbacks. While we have a remarkable Plant team who works very hard, they also have acres of other parts of the nursery to tend to as well as research trials to investigate. We think this problem is very relatable to you, green industry professionals. So, after each cut, the plant returns, quicker than anyone would like, and basks in the glory of our sun, feeding the root system until we rush back outside and cut it back before it goes to seed in fall. There is but one victory - the Canada goldenrod has not seeded around the rest of the property and is mostly contained in one bioswale. But it is a pyrrhic victory, the plant lying in wait for us to forget it for one season too long before it fulfills its manifest destiny and overtakes its goldenrod comrades, winning the war.
 
Why don’t we just spray it or dig it out and remove it? Well, folks, how do we gain the experience to tell you the good, the bad, and the ugly about plants if we aren’t toiling right alongside you?
 
So let this be a warning to you.
 
Cutbacks can work - if you stay on top of them.
 
Otherwise, you may want to consider a different strategy.

 

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