Restoring and managing native ecosystems in the Driftless Area can be a challenge. On any given 50 acres the topography, soil type, and plant species can vary dramatically. Within a short distance, soil can fluctuate from dry and rocky to wet mesic, with oak savannas and oak-hickory woods vying for space with invasives like the multiflora rose, bush honeysuckle, autumn olive, and brambles.
Overgrown oak savannas, woods, and prairies are not necessarily or solely caused by fire exclusion. The introduction of non-native, invasive woody plants has altered our ecosystems. They displace native plants and need removal to restore a healthy balance. Removing them by historical methods hasn’t proven effective, but understanding their biology and applying a targeted method can create the desired result.
What is resprouting?
The difficulty in removing unwanted, woody plants is their resprouting growth. This growth is dominated by a central growing stem, this process is called apical dominance. When the central growing stem is intact, it prohibits other growth. Once that central stem is damaged, the plant faces a fight-or-flight response but without the ability of flight it fights by producing multiple stems below the damaged area. These stems, known as the resprouting growth, develop their own apical dominance and the pattern repeats with each disturbance. This is what makes non-native, invasive plants particularly troublesome. Click here for a detailed explanation of the biology and the hormones that create the balance.
The Search for Answers
Tackling these unwanted resprouting woodies within our limited resources (time and money) required some research. I consulted research papers and talked with other restoration practitioners. Anecdotal accounts have some educational value but what worked on one parcel of land at one particular time might not work on another – a universal truth of nature!
One landowner burned annually then trudged through the leg-cutting canes of the top killed brambles herbiciding the resprouts. Year after year after year the intense emotions of charring the land and laying out copious amounts of herbicide were felt. Why weren’t there positive results?
Many tout the use of annual or frequent burns to top kill unwanted brush, thinking it “sets them back” or stunts their growth. Top kill gives the illusion of effectiveness but it’s a temporary effect and this frequency of fire has steep trade-offs that result in decreased biodiversity. Annual burns to control resprouting woodies is like painting over the spot on the ceiling when the roof leaks. Each time it rains, the spot returns. Why not fix the roof and not concern yourself with the leak for the next 15-20 years?
In another oak savanna, managers mowed several times a year as the sole management activity. Cool season grasses became dense and lush. Once the mowing stopped, the resprouting woody growth grew profuse and luxuriant. After over ten years of mowing, there was little evidence the roots were sapped of their nutrients and weakened.
We scratched our heads. These generally accepted methods weren’t working. The science – the biological science of apical dominance — had been ignored.
By coupling the science with possible management techniques, an effective method for “fixing the roof” was found – cut and treat. This method uses chainsaws and loppers to “cut” the stem(s) at the base of the target plant, then “treat” the cut end with a spritz or dab of herbicide. We use a 20% mixture of Progeny® brand herbicide in bark oil. This herbicide is effective on the cut stumps and uses less herbicide than similar chemicals mixed with water for foliar spray. We did not need to retreat the original cut plant but if the infestation is dense, a second year of foliar spraying reprouts can be expected.
Once cleared using the cut and treat method, our experience is the land requires little follow-up maintenance for resprouting woodies. The time spent in the beginning by cutting and treating has decreased expenses and time in subsequent years. There was no risk of biodiversity losses associated with annual burns, no risk of increasing cool season grass growth with mowing during the growing season, and less risk of an immediate wholesale return of the invasive resprouting woodies if management were to stop.
Science prevails! Unless the biology of resprouting changes, the science cannot be discounted.