A Management Guide for Invasive Plants in Southern Forests James ...

2Over the past 50 years, the explosion in the number of ornamentaland horticultural species and abundant varieties has yielded benefitsto many aspects of modern society, such as landscape beautificationand rapid-growing shade trees and shrubs, but have taken their tollon our natural ecosystems. The social costs of annual maintenancecontrol of these introduced invasive species have skyrocketed in ouryards, parks, green spaces, and along rights-of-way as well as forests,grasslands, and wildlands.Nonnative plants become invasive for many reasons. The followingare among the traits that help nonnative species establish and spread:• Early introduction in the 1700s and 1800s as ornamentals orforages, resulting in a long period of spread, hybridization, andadaptation (Hundreds of thousands of small farmers plantedornamentals around their houses, and the plants remained afterthe great exodus in the late 1800s and early 1900s to cities.)• Rapid early growth rates that outpace native cohorts• Few native predators and a resiliency to predation by insects,pathogens, and mammals• Production of abundant fruit and seed at a young age• Seed that is readily spread by wind,water, birds, and mammals• Seed that can remain viable inthe soil for 1 year and even up todecades• Roots or rhizomes that persistand resprout after topkill followingherbicide applications, cutting, orburning and that grow outwardto yield intensified and denseinfestations• Capability to establish and spread insites of periodic disturbance, such asalong ever expanding forest edges,on rights-of-way, along stream andriver banks, and in abandoned cropand pasture landsCogongrass seedheads.Nonnative shrub production.Old homestead with wisteria and privet.Jeff Sibley• Capability to adapt and spread in a new site through a “set-and-wait”strategy until conditions are suitable• Wide tolerance to shade, drought, soil conditions, and flooding thatgives a decided advantage over native plants• Capability of forming exclusive (or limited species) dense infestationsthrough their high amount of leaf area that is often evergreen orappears earlier in spring and sheds later in fall compared to native species• Capability of suppressing other plant seed germination and growth byreleasing allelopathic chemicals (through the invasive plant’s foliageand roots)• Alter biogeochemical cycles and soil micobial communities that favorinvaders over native plantsBamboo rhizomes and roots.The more of these traits a nonnative species might have, the greater itslikelihood of success in establishing itself and spreading, as well as resistingcontrol and eradication.