Aspen shoots, often called suckers, are a common and aggressive landscaping problem that signals a widespread issue beneath the soil. These shoots are not individual seedlings but sprouts from the extensive, shallow root system of a parent tree, making them difficult to eliminate permanently. The underlying structure of the aspen means that a coordinated, multi-step approach is necessary to gain control over this pest. This article details the proven methods required to stop the growth of these shoots.
Why Standard Removal Fails
Aspen trees reproduce primarily through root suckering, establishing themselves as a single, large clone connected by a massive underground root network. This expansive network can stretch for dozens of feet, allowing the clone to rapidly colonize an area. When the main stem is cut or the shoots are simply mowed down, the plant’s internal hormonal balance is immediately disrupted.
Removing the above-ground trunk eliminates the source of auxin, a hormone that normally suppresses the growth of dormant root buds. With this inhibitory signal gone, the ratio of growth hormones shifts, stimulating the widespread activation of dormant buds on the lateral roots. This biological response is the tree’s survival mechanism, causing it to produce a sudden and often thicker flush of new shoots. Consequently, simple cutting or mechanical disturbance only makes the problem worse, resulting in a dense thicket of new growth.
Targeted Chemical Treatment Strategies
Permanent elimination requires systemic herbicides that can travel through the vascular system and kill the entire root clone. The most effective active ingredients for this task are glyphosate and triclopyr, which must be applied directly to the plant’s living tissue to be absorbed and translocated throughout the root system. Proper application is paramount for success, requiring specialized techniques to bypass the thick bark and reach the active cambium layer.
Cut-Stump Treatment
The cut-stump treatment is highly effective for individual shoots or small trees. A concentrated herbicide solution is painted or dripped onto the freshly cut surface immediately after felling. The treatment must cover the thin, moist ring of cambium just beneath the bark, as this is the vascular tissue responsible for transporting the chemical down to the roots. If the stump dries out, the vascular tissue seals, preventing the required downward movement of the herbicide.
Hack-and-Squirt Method
For larger trees, the hack-and-squirt method, also known as the frill method, creates direct entry points for the chemical without removing the entire tree. This involves making a series of downward-angled cuts around the entire circumference of the trunk with an axe or hatchet, penetrating the bark and cambium layer. A small dose of concentrated herbicide is then squirted or poured directly into each cut, ensuring the chemical is distributed evenly around the stem.
Basal Bark Treatment
An alternative for smaller stems or thin-barked suckers is the basal bark treatment, which uses an oil-soluble formulation of triclopyr mixed with a penetrating oil carrier. This mixture is sprayed or painted completely around the lower 12 to 18 inches of the stem, saturating the bark down to the root collar. The oil carrier is formulated to penetrate the intact bark and deliver the active ingredient into the phloem, allowing it to travel to the root system.
Intensive Mechanical Suppression Techniques
For those who prefer not to use chemical agents, mechanical methods offer suppression, though they are often more labor-intensive and require sustained effort. The goal of these techniques is to physically exhaust the root system’s stored energy reserves. Merely pulling the shoots is ineffective, as the root remains intact and will simply sprout again.
Root Barriers
To physically prevent emergence in a localized area, a root barrier can be installed by digging a trench and placing a thick plastic or metal sheet vertically in the soil. Because aspen roots are relatively shallow, a barrier installed to a depth of at least 24 inches can effectively block the horizontal spread of new shoots into a protected zone. This technique is best suited for containing the problem rather than eliminating the entire clone.
Intensive Root Removal
Intensive digging and removal of the lateral roots, where the sucker buds reside, is a direct but arduous method of control. This involves carefully excavating and cutting out sections of the shallow root system, which typically lie within the top 12 inches of soil, to remove the source of the sprouting. This physical wounding must be extensive, as any remaining root fragment can still produce new suckers.
Smothering and Solarization
Smothering and solarization use physical barriers to starve the root system of light and oxygen. Laying down heavy, opaque materials like black landscape fabric or tarps and covering them with a thick layer of mulch over the affected area can suppress new growth. This treatment must be maintained for at least one to two full growing seasons to fully deplete the stored carbohydrates in the roots.
Optimal Timing and Follow-Up Care
The success of a systemic herbicide application is heavily reliant on the timing, aligning the treatment with the tree’s natural physiological cycle. The most effective window is in the late summer or early fall, typically from August through October, before the first hard frost. During this period, the aspen is no longer actively growing new leaves but is instead preparing for winter dormancy.
In preparation for the cold season, the tree actively transports sugars and other vital nutrients down from the leaves to be stored in the root system. Applying a systemic herbicide during this downward flow ensures the chemical is effectively pulled deep into the extensive root network, maximizing the kill of the entire clone. Treatment outside this window, such as during the spring when sap is flowing upward, will generally result in poor translocation and limited root kill.
Safety precautions are necessary during application, including wearing appropriate personal protective equipment like gloves and eye protection to minimize exposure. Care must be taken to prevent herbicide drift or runoff that could injure or kill desirable plants in the vicinity. The process of eliminating an aspen root system is rarely a single-step fix, so monitoring the area is important, as new shoots will likely emerge in the following season. These subsequent sprouts must be treated immediately upon appearance to deplete the remaining root energy and finally achieve permanent control.