A Prescription of Fire for Sweetgum Ire
If you are managing land for wildlife in the Southeast and are reading this blog, we almost certainly have something in common. I’m referring to the ire for the infamous American sweetgum (Liquidambar styraciflua). They are one of the most hated native trees in the country, and undoubtedly one of the most likely to survive a nuclear winter or a “Planet Killer” meteorite.
For those of you who aren’t familiar with the American sweetgum and are asking yourself, “Why not just cut them down, or better yet, mow them down while they are young?” Countless times, landowners and managers have uttered the words, “Oh, if only it were that simple!”
You see, sweetgums are like glitter or herpes: once you have them, you have them for life. They would love nothing more than for you to chop it down or mow it while it’s young. Their roots can travel dozens of feet just beneath the surface of the soil. When the top of the tree is cut, a signal is sent, and the tree’s energy is redirected to those roots to produce what we call “root suckers.”
One root can produce a seemingly endless number of these root suckers, which become their own trees and produce more roots with the potential to send up even more suckers. Even if you cut a root away from the tree, it can have enough stored energy to produce new root-sucker trees. Cutting or mowing a small patch of sweetgums will quickly lead to a thicket that will soon outcompete and shade out any beneficial plants and trees in the landscape.
So, you might ask, “How do I get rid of sweetgums? What are my options?” Fortunately, there are a couple of options for killing or, at the very least, controlling sweetgums. More important than which option you choose is when you choose to use it.
Herbicide is probably the most popular option, either applied by spraying the foliage with a backpack, boom, or, nowadays, aerial drone sprayers, or by an increasingly popular method called “hack and squirt.” This is by far the most effective and environmentally friendly method, but it is also by far the most time consuming. If you have any amount of acreage, this method will be mostly reserved for mature trees.
Spraying is a more efficient method, but large scale spraying of herbicide isn’t ideal if you are managing for native plant diversity, as herbicides are notorious for killing beneficial plants and trees along with the targeted species. Not to mention the downstream effects of large scale herbicide use.
Don’t get me wrong, I’m under no illusions that herbicides are a valuable tool in the toolbelts of land managers, but most would agree that less is better.
The other option is prescribed fire. Fire is far and away the cheapest, least laborious, most environmentally friendly, and actually beneficial tool for sweetgum control. Thankfully, prescribed fire is making a comeback in popularity in the world of land and forest management.
Fire has been used for thousands of years in North America by Native Americans to sculpt and generate the Southern pine and oak savannas that were so prevalent and vast that, when Europeans arrived in the Southeast, it was said that a squirrel could make it from the coast to the mountains without ever touching the ground beneath.
Over those thousands of years of prescribed fire on the landscape, many native plant species and their seeds became dependent, either partially or completely, on fire to allow for germination and regeneration. With plants’ dependence on fire came the dependence of the animals that used these plants for food and cover, namely, ground nesting birds like quail and turkeys.
Here’s the catch, most of the prescribed burning that goes on today is done in the dormant season. While this is still very beneficial for the health, regeneration, and proliferation of the native forbs and grasses that we want on the landscape, it doesn’t do much to speak of when it comes to sweetgum control. And if the sweetgums aren’t eliminated or drastically stunted, the light needed for these beneficial native forbs and grasses to grow never makes it to the forest floor.
The old saying, “timing is everything,” rings true here. If your goal is to damage and eventually kill sweetgums while simultaneously boosting the quantity and diversity of your beneficial native plants, a late-growing-season burn is what you want. August–October is the perfect window.
This is a time when the Sweetgums have used up most of their energy making leaves and branches throughout the spring and summer and are just beginning to move nutrients back down to the roots. Catching them with a good burn at this critical time will drastically reduce their root carbohydrates. This will lead to a much higher mortality rate and much weaker, stunted resprouts.
If this method is applied in consecutive or alternating growing seasons over a two- to three-year period, you can successfully exhaust the sweetgum’s root-stored energy and kill the trees. Now that they are gone and you’ve put fire back on the landscape, your beneficial native plant diversity will be primed to take over and shade out any future unwanted sweetgum or other hardwood growth, especially with a regularly implemented prescribed burn routine.
SIDENOTE: It’s just fun to (safely) light the woods on fire and hear the crackle of the boiling sweetgum sap popping the bark right off the tree!! Be safe, and happy burning!
—Interlaken Wildlife Team
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