How to Kill Invasive Trees

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Roger Culpepper, host of Pay Dirt on Realtree 365, shares an easy method for stopping sweetgums and other problem trees

Learn how to control invasive vegetation on Realtree 365's Pay Dirt.

There are plenty of good reasons to kill a bad tree. If you’re a wildlife habitat manager, selectively eliminating low-value trees – essentially, those that have little mast production or timber benefit – is one of the most cost-efficient things you can do to improve your property. Removing those trees reduces competition for the quality trees you do want to nurture and opens the understory to more sunlight, which stimulates the new growth that all kinds of critters need. 

In an existing, mature forest where the goal is to enhance the best trees, this practice is called Timber Stand Improvement (TSI). If you’re a landowner planning to one day harvest your timber, your best bet is to consult a forester before planning a large-scale TSI project. Foresters can help you identify those low-value trees, which include species that don’t produce mast or valuable timber, as well as scrubby or malformed trees of a beneficial species that compete with high-quality trees.  

Beyond dropping the spiked gumballs country kids sometimes collect to throw at the cat lady’s car, sweetgums have little value.

In other, more open areas, landowners frequently find themselves with patches of saplings that have grown out of control. This usually happens in old fields that haven’t been disturbed in a few seasons, or after timber cutting operations. Like many land managers in the Southeast, Roger Culpepper, longtime keeper of Realtree Farms and co-host of “Pay Dirt” on Realtree 365, finds himself in a constant struggle with fast-growing sweetgum trees. “Sweetgum and cockroaches,” he says. “Two of the only things left after an atomic blast.” 

Beyond dropping the spiked gumballs country kids sometimes collect to throw at the cat lady’s car, sweetgums have little value. But left alone, they can overtake early successional habitat and young forests in only a few growing seasons, quickly becoming too large to kill by mowing or with prescribed fire. Even if you can mow those small saplings, the stumps usually survive, grow new shoots, and remain tire-puncturing hazards years later. A flat tractor tire stalls mowing progress, and the next thing you know, those sweetgums are left to grow another year. That’s how problems begin, and why a lot of mowed sweetgum patches eventually become impenetrable sweetgum thickets. 

To actually kill the young trees, Culpepper keeps a spray bottle of herbicide handy – he likes high-concentrate glyphosate – as he cuts the trees down.

“The stumps will gloss over after the tree is cut, forming a protective coating, within about 30 minutes,” he says. “Once that happens, spraying them doesn’t do any good. But if you hit the stump with that spray immediately, it takes it down to the roots, and you can kill it then.” 

In this episode of “Pay Dirt,” Culpepper is working with a machete and backpack sprayer of herbicide, but you can cut down small trees however you like. A chainsaw, provided you know how to use it safely and correctly, is easier and faster. 

Hack and squirt is a common method used in TSI. (Bill Konway photo)

Larger trees that are potentially dangerous (and time consuming) to cut down can be killed by girdling them with a chainsaw and treating that cut with herbicide. Girdling involves separating the bark and outer rings of the tree without cutting through the trunk. This circular cut itself will eventually kill the tree, but not right away, and maybe not down to the stump. Adding the herbicide helps it along. Use the top edge of your chainsaw to slowly walk around the tree trunk, cutting a ring (1 inch or a little more) as you go. The cut should be parallel to the ground and join back where you started it. Once that’s done, quickly spray the cut with the herbicide. That’s it. 

An even easier option for larger trees is to hack a few deep cuts — through the cambium layer of the tree — into the trunk, and then inject those cuts with herbicide. You need the cuts to be deep enough to cup and hold the herbicide in place. This method, called hack-and-squirt, works, although many consider girdling to be the surer bet. 

Glyphosate is the active ingredient in Roundup, and it’s an all-purpose herbicide that will work for these chores. It can be purchased in generic form by the gallon at most farm and home stores. Culpepper recommends adding dye, so that you can take note of which trees have been treated as you work (he also likes to work in pairs; one person cuts while the other sprays). Specialty herbicides, such as Tordon RTU, are actually made for the task and come pre-dyed. Check your state regulations and follow the application instructions on the bottle before using any type of herbicide. Especially the specialty stuff.  

Aside from early spring, when high sap content can make it difficult, you can kill bad trees just about year-round. Culpepper’s working through the heat of the Georgia summer in this video. But the results will be the same in the winter and you’ll sweat a whole lot less. It gives you a good reason to be outside when there’s not much else to do, and it helps make your property better. What’s not to like? 

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