When aggressive plants establish themselves, they often develop woody stems and deep, extensive root systems that resist standard hand-pulling or casual mowing. These unwanted invaders are typically not delicate annual weeds but rather tenacious perennial saplings or vigorous volunteer seedlings that are determined to grow into full-sized trees. Dealing with these woody invaders requires methods specifically designed to eliminate the root structure, which may involve specialized mechanical effort or targeted chemical application.
Identification of Woody Invaders
The first step in effective removal is accurately identifying the specific woody invader, as its growth habit dictates the best eradication strategy. Common culprits include highly aggressive, non-native species like Tree of Heaven (Ailanthus altissima), known for its rapid growth and prolific root suckering. Certain native plants, such as sumac (Rhus species), also spread aggressively through rhizomes, creating thickets of what appear to be multiple individual saplings.
Other frequent offenders are volunteer seedlings from nearby mature trees, such as maples, oaks, or elms, which develop a strong, deep taproot quickly after germination. Aggressive woody vines, like certain types of bittersweet, can also develop thick, tree-like stems that require similar removal techniques. A plant that spreads primarily through root suckers, like sumac or Ailanthus, demands an approach that treats the entire connected root system, rather than just the visible stem. Conversely, a plant with a single, deep taproot, such as a large oak seedling, may be susceptible to deep digging if caught early enough.
Non-Chemical Removal Methods
For those avoiding chemical solutions, mechanical removal requires significant effort focused on completely extracting the underground structures. Small saplings with a single stem and a developing taproot can be removed by digging deeply around the plant, ensuring the entire root mass is lifted intact. Because woody plants quickly develop strong root systems, this often involves using specialized digging tools like a mattock or a sturdy shovel to sever all lateral roots before attempting to pry out the main taproot. If any portion of the taproot remains in the soil, particularly the crown where the root meets the stem, the plant retains the ability to sprout new growth.
Repeated cutting or mowing is a technique that attempts to starve the root system by continually removing the above-ground foliage necessary for photosynthesis. This method is only effective if performed relentlessly over several growing seasons, as the plant will repeatedly draw on stored root energy to regenerate. If the cutting is not frequent or low enough, the plant will simply establish a dense, bushy form, making the problem worse and making future removal more difficult.
For larger woody stems that cannot be dug out, girdling offers a way to mechanically kill the tree or large sapling slowly. Girdling involves removing a continuous ring of bark and the underlying phloem layer completely around the circumference of the stem. This action prevents the carbohydrates produced in the leaves from reaching the roots, effectively starving the plant’s underground structures. The root system will die over a period of 6 to 18 months, depending on the species and size, after which the dead trunk can be safely removed.
Targeted Herbicide Application
When dealing with highly regenerative species or numerous thickets, targeted herbicide application is often the most efficient way to achieve complete root death. The most effective method is the cut-stump treatment, which involves cutting the woody stem close to the ground and immediately applying a concentrated herbicide to the freshly exposed surface. The application must be done within minutes of the cut before the plant seals the vascular tissues.
The herbicide should be applied to the cambium layer, the thin, active ring just beneath the bark, as this is where translocation downward to the roots occurs. Herbicides containing active ingredients like triclopyr or glyphosate, labeled for brush or stump killer use, are necessary for penetrating woody tissues and reaching the root system. This technique ensures the chemical is contained and minimizes the risk of non-target plant damage.
Another effective technique for smaller stems (less than 6 inches in diameter) is the basal bark treatment. This method involves spraying an oil-soluble herbicide, typically triclopyr ester mixed with a penetrating oil, directly onto the bark around the entire circumference of the lower 12 to 18 inches of the trunk. The oil carrier allows the chemical to penetrate the bark and move into the plant’s vascular system, killing it without cutting.
For maximum effectiveness, chemical applications should ideally be performed in the late summer or fall. This is when woody plants are naturally moving sugars and nutrients down to the roots for winter storage. This natural downward flow, known as translocation, efficiently carries the herbicide to the root system, resulting in a more complete kill. Always use appropriate personal protective equipment (PPE), including gloves and eye protection, and strictly follow the product label instructions.
Preventing Regrowth and Future Infestations
Once the initial removal is complete, long-term vigilance is necessary to prevent the establishment of new woody invaders or the regrowth of treated ones. The most immediate concern is monitoring the area for root suckers, which emerge from the remaining root system. These suckers must be treated immediately with targeted chemical applications or severed below the ground surface as soon as they appear to deplete the root’s energy reserves.
Preventing new seedlings from establishing requires controlling the soil environment, often by applying a thick layer of organic mulch, ideally 3 to 4 inches deep, which suppresses seed germination. Establishing a dense, competitive groundcover that shades the soil can also successfully outcompete new woody seeds. Finally, identify and remove the parent plant or nearby seed sources, which are the ultimate cause of repeated infestations, to significantly reduce the flow of new seeds into the area.