Undergrowth in Pennsylvania forest

Forest Undergrowth & Vegetation Management

Owning woodlands can be rewarding in so many ways but also presents numerous challenges that every forest owner can relate to. One such challenge is managing the forest undergrowth and vegetation. Managing the forest understory is an intricate task which requires a balance of practices that are aimed at preserving ecological harmony, strengthening forest health, supporting biodiversity, and increasing overall forest production. The key components in undergrowth management include managing competing plants, utilizing herbicides for the elimination of unwanted species, and conducting prescribed burns to control vegetation. The different techniques used to manage the understory can be categorized into manual, mechanical, biological, and chemical measures, but the best method in most scenarios is one that uses an integration of many techniques. In this article, we are going to discuss some of the most important aspects of forest undergrowth and vegetation management.

Understanding & Managing Competing Plants

Forest ecosystems are highly complex with diverse species, each contributing uniquely to the ecological balance. In a private forest, there are always favoured species that contribute to the overall production of the forest, mostly timber. However, certain plants – often termed “competing plants” – can hinder the growth of the favoured species, particularly during the forest’s regeneration phase. As a private forest owner, understanding the dynamics of these plants is crucial for effective forest management.

Competing plants are mostly early-succession plants. This means that they establish quickly on disturbed sites and can easily outpace the regeneration of the desired tree species in terms of resource utilization such as light, water, and nutrients. For instance, Japanese stiltgrass (Microstegium vimineum) is a competing and invasive plant found in Pennsylvania and all over the United States that inhibits the growth of native plants, including tree seedlings. The effect of these competing plants is not limited to tree growth. They also affect the biodiversity of the forest. For instance, the dead stalk of the same Japanese stiltgrass forms a very thick mat on the forest floor that inhibits the movement of reptiles and amphibians.

Identification of the competing plants and their ecology allows us to tailor a management plan which uses one or more of the methods. One of the most effective methods of dealing with competing plants includes managing the light penetration into the forest floor by selectively thinning the canopy. Coming back to our example of Japanese stiltgrass, mechanical removal techniques like mowing or string trimming are recommended. But the timing of these operations is also very important, which is why it is crucial to follow a tailored management calendar for that species and particular forest site.

Using Herbicide to Control Undergrowth and Unwanted Species

While mechanical removal of unwanted species can be effective, there are scenarios when it may not be sufficient to control the growth of such species, especially if they are already spread across a large area, or if they are recurring, meaning they grow back once removed mechanically. In these cases, herbicides can be an invaluable tool as a part of an integrated vegetation management strategy.

Herbicides that are forest labelled are effective and environmentally friendly, but like herbicides used in agriculture, the use of herbicides in forests remains controversial. Nevertheless, as forest owners are encountering more problems with increasing intensity like increasing invasive plants, declining pulpwood markets, poor harvesting practices, pest infestation, and poor forest regeneration, more and more forest owners are turning towards herbicides for vegetation management. Similarly, herbicides are being proven safe and effective means of solving all these problems.

Choosing the correct herbicide, the rate of application, method of application, and timing are crucial for maximum effectiveness and can only be achieved by careful assessment of the objectives. However, the best way to use herbicides in your forest as a forest owner is to consult experts while choosing the herbicides and then to follow the labelled instructions which can be found in all types of herbicides. The selection and timing of herbicides can be illustrated in the same example of advanced Japanese stiltgrass invasion, where prodiamine or pendimethalin are used as a preemergence treatment in late winder or early spring while glyphosate or quizalofop are used as a postemergence treatment in Mid-May through August.

Finally, in addition to combining herbicides with other methods, continuous monitoring of the forest ecosystem for any signs of negative impacts or side effects from the herbicide is also recommended.

Controlled Burning as a Vegetation Management Technique

“Fire is a bad master but a good servant”. This old saying perfectly sums up the relationship of fire with forests. With rising temperatures and changing climate, the age-old risk of forest fire has become more serious than ever. And one of the main objectives of managing understory vegetation in forests all around the world is precisely to reduce the risk of forest fires. However, controlling and guiding fire to serve us is one of the most effective methods of managing forest undergrowth and vegetation.

It is also a traditional practice and involves the intentional burning of forest undergrowth under controlled conditions, serving multiple purposes: reducing the buildup of fuel on the forest floor, controlling pests and diseases, and promoting the growth of desired species by removing competing and invasive plants. The factors that need to be controlled or considered are weather conditions, wind direction, smoke management, firebreaks, necessary equipment, personnel, and a contingency plan. It is also a cost-effective and faster way of getting rid of competing plants and unwanted vegetation. In some cases, prescribed burning is also done to induce regeneration of desired species because some trees like pine require fire to regenerate.

Moreover, it is also very important to recognize the law and regulations regarding prescribed burning which will vary from one state to another and even within states. As a private forest owner, it is your responsibility to adhere to these regulations, which is why consultation with local authorities or experts can ensure safety and lawfulness.

Finally, there are region-specific fire standards developed, such as Pennsylvania prescribed fire standards, which outline the process of planning as well as implementation for using prescribed burns.


To sum up, forest undergrowth and vegetation management is a crucial part of sustainable forest management because it directly shapes the forest’s health, biodiversity, production, and survival. By understanding and effectively controlling competing plants, judiciously using herbicides, and conducting controlled burns, you can maintain and enhance your forest’s health and resilience. However, these are complex tasks, and it can be beneficial to seek expert advice or assistance when necessary. Doing so can not only protect and preserve your forest for your enjoyment but also contribute to broader ecological health and biodiversity.

Contributed by Sandesh KC

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