Alien Threats to Southern Indiana's Forests

Non-native invasive plants occur throughout the Hoosier National Forest.  A comprehensive inventory for non-native invasive plants across the Hoosier is not yet completed, but surveys have occurred in all of the designated Special Areas and the Charles C. Deam Wilderness (Hedge and Homoya 2000; Hedge 2002).  Ongoing and future invasive plant surveys will continue, and adhere to standardized Forest Service protocols for invasive plant inventories.

Nearly all the invasive plants documented on the Forest typically occur in openings or prefer open habitats.  Many of these species exist primarily along roadsides or old fields.  These plants may invade forest communities, but species intolerant of shade would decline as the forest ages through natural succession.  Some of these invasive plants first establish along roadsides, but also have the ability to grow and invade the nearby forest.  The species that are adapted to both open and closed canopy conditions, as well as others having preferences for closed conditions, are the most difficult plants to control and the greatest concern on the Forest.  Generally, invasive plants have a tendency to invade natural communities along disturbance corridors such as roads and trails.  Invasive plants have spread across the Hoosier National Forest by a variety of methods, including unintentional movement by people on their clothes or vehicles.  Birds disperse many species such as honeysuckles by eating their fleshy fruit, while others spread via wind, animals, or water current.  The establishment of some invasive plants occurred because of earlier planting by landowners prior to the Forest Service acquiring those lands.  In some cases they look very similar to native species and may even hybridize with native species. The American and Oriental Bittersweet is an example of this.

The table below of Non-native Invasive Plants of Concern, is a prioritized list of species with documented infestations on the Hoosier National Forest.  The species presented in the table is not a complete account of all known invasive plants on the Forest, but it does contain those species already known to be of some concern.  Undoubtedly, future inventories will discover new invasive plant infestations that immediately become a high or medium threat, while others on this initial list will decline to a low priority because of successful control measures.

Two recent inventories for invasive plants in selected areas of the Hoosier National Forest provided the primary basis for inclusion on this list (Hedge and Homoya 2000; Hedge 2002).  These inventories also documented five other invasive plants as occurring on the Forest, but reported that they were a low threat to native biological diversity.  In addition, Hoosier National Forest botanists and biologists have observed another 44 species, but we consider these invasive plants as a lower priority for treatment.  A large number of these species are introduced pasture grasses or other plants typically found in old fields or homesteads.  Most of these invasive plants are problems only where they occur.  All but two of these invasive plant species with known infestations on the Hoosier, have their origin from outside of North America in Europe, Asia, or Africa.   

                           Non-native Invasive Plants of Concern

References

Hedge, Cloyce. 2002. Inventory and Control Recommendations for Invasive Plant Species on Selected Areas of the Hoosier National Forest. Indiana Department of Natural Resources, Division of Nature Preserves.  Unpublished report. [On file with:  Forest Supervisor, Hoosier National Forest, 811 Constitution Ave., Bedford, IN 47421]. 12 p.

Hedge, Cloyce and Mike Homoya. 2000. Surveys for Invasive Plant Species on Selected Areas of the Hoosier National Forest (with recommended control measures). Indiana Department of Natural Resources, Division of Nature Preserves.  Unpublished report. [On file with:  Forest Supervisor, Hoosier National Forest, 811 Constitution Ave., Bedford, IN 47421]. 20 p., plus appendixes.

Top Most UNWANTED Invaders in Southern Indiana:

• Bush Honeysuckle

• Emerald Ash Borer

• Garlic Mustard

• Japanese Honeysuckle

• Japanese Stiltgrass

• Kudzu

• Sudden Oak Death

• Tree of Heaven

Selected Success Stories on Nonnative Invasive Species

	Workshop Discusses, Eats, and Plots Against Alien Invasives The Hoosier National Forest was a sponsor of a successful workshop to raise the awareness of the threat of alien invasive species in southern Indiana. Landowners learned to identify invasive plants,
	Non-Native Invasive Plant Partnership Between Hoosier NF and Indiana University Participating agreement results in a four-prong approach to give elementary school students a better understanding of invasive species.
	Remembering the Environment & Mom The Hoosier National Forest puts up boot brush stations at trailheads to reduce the spread of non-native invasive plants.

Link to Region 9 US Forest Service Nonnative Invasive Species webpage

Link to National Celebrating Wildflowers webpage