Invasive and Competing Plants

Competing and invasive vegetation in forests can impact both regeneration success and biodiversity. Private forest owners can access Penn State Extension’s resources to learn more about invasive forest species and competing plants, identification, and control tips. Information on Integrated Forest Vegetation Management and herbicide control is also available here.

Invasive Forest Species

Invasive species infestations are among the most significant issues affecting US landscapes. In the forest ecosystem, invasive species can manifest as various non-native plants, pathogens, and animals.

Such infestations pose a serious threat to the forest’s biodiversity and ecological integrity. Left untreated, these species can result in the destruction of wildlife habitats, reduced forest productivity, and diminished land value.

Invasive vines are some of the more common invasive forest plants. Grapevines, for instance, grow into the tops of trees and can cause disfigured trees, as well as block light and slow the tree’s food synthesis. Vines such as mile-a-minute and oriental bittersweet can create dense foliage that blankets and gradually suffocates native vegetation.

Other noxious weeds found in Pennsylvania forests include the Japanese barberry woody plant, multiflora rose, and various privet shrubs. Tree-of-heaven is another rapidly growing invasive tree and noxious weed. The tree’s extensive root system makes it difficult to control, but applying systematic herbicides at the optimum time can be effective.

Managing Competing Plants in the Forest

Protecting forests from natural threats such as diseases and competing plants is an integral part of forest management. Plants competing for space, water, and nutrients can affect timber stand development, along with the biological diversity of native plant and wildlife species.

To sustain a healthy and productive forest ecosystem, it’s important to consider vegetation management practices using an Integrated Vegetation Management (IVM) approach. IVM provides a way of managing vegetation through various methods, including herbicide application.

When properly applied, herbicides can be a safe and effective method for managing and controlling forest vegetation. When controlling unwanted trees, hack-and-squirt herbicide applications are among the most target-specific and economical means. Other types of herbicide applications include tree injections and basal bark sprays.

Forest Regeneration

Allowing forests to regenerate after harvesting is an essential aspect of sustainable forestry. Various factors, however, can interfere with forest regeneration and, eventually, threaten forest sustainability. These include competing plants and deer populations.

Treating competing vegetation before harvest is crucial for preventing post-harvest problems such as impeded access and damage to desirable species. If deer damage to the forest is severe, reducing populations might be necessary. Methods to consider include seedling protectors, fencing, and deer repellents.

While most forests regenerate without human intervention, planting trees can accelerate the natural progression and enrich a newly regenerating forest with an uncommon species. Learn more about establishing wooded areas on rural properties with Penn State Extension’s Guide to Tree Planting Success.

On this page, forest landowners can access resources on controlling invasive and competing species. Information is also available on understanding best management practices for PA forests and creating a forest stewardship plan.