Invasive species

Any plant that grows outside of its natural range is considered exotic. If it responds to its new environment with rapid growth, and if it can quickly establish itself over large areas of land then it is considered invasive.

How does this happen?

When humans were introduced into North America we brought plants with us from our country of origins. Plants have

been introduced for agricultural purposes, horticultural purposes, and in some cases, purely by accident. However, when

a plant species is introduced outside its natural range, it is also outside the natural range of its natural controls that can

include any herbivores, parasites and diseases. Free from these natural controls, some exotic plants experience rapid

and unrestricted growth, become invasive in their new environments, and reduce ecosystem diversity and function.

Why aren't’t all exotic plant species invasive?

The primary factors which contribute to a plant’s ability to invade include its life cycle, annual or perennial; how it

spreads, as a vine or by seed; its capacity for abundant seed production; its high seed germination rate; how long-lived

its seeds are; and how rapid it can mature to its seed-producing stage. The quicker it can reproduce itself, the quicker it

can invade and overwhelm the native plant species which previously occupied the land.

Why should we be concerned?

Invasive plant species are the second greatest threats to the natural ecosystems of the world today. Only direct habitat

destruction poses a greater threat to the future of biological diversity. Invasive species disrupt the ecology of natural

ecosystems by displacing native plant and animal species and reduce biological diversity by reducing the amount of light,

water, nutrients and space available to native species.

What Plants are Invasive in Northeastern Ohio?

 

 

 

For more Information:

• Ohio Invasive Plant Council 
• Midwest Invasive Plant Network
• Plant Conservation Alliance

Invasive Insects and Diseases

The introduction of exotic plant species have resulted in the escape of plant pathogens that have greatly impacted our local flora, such as Dutch Elm Disease, Beech Bark Disease, Chestnut Blight and Dogwood Anthracnose. Introduced insects that have impacted Holden include European Beech Scale, Gypsy Moth and Emerald Ash Borer.

Introduced Animals

White-tail Deer were extirpated from Ohio in the late 1800s but were re-introduced to Ohio in the late 1920s. Browsing by white-tail deer has a negative impact on all Holden collections. Deer browse destroys specimens propagated or purchased for the designed landscape. Browsing severely limits ecological function of natural areas when whole age classes and layers of woody species disappear from the landscape. Holden has protected a landscape matrix of woodland and grassland that is coincidentally optimal habitat for whitetail deer. Deer exclosure studies within the natural landscape produce quantifiable data on the impact of whitetail deer on the landscape. Infrared aerial surveys document the population density of whitetail deer in and around the Holden landscape. Historical density for whitetail deer in northeastern Ohio is eight deer per square mile. Current whitetail deer density is 29 deer per square mile. Whitetail deer are one of the strongest negative pressures on Holden landscape and require management plans to reduce population density.

Earthworms

Did you know that there are no native earthworms in glaciated North America? For many of the same reasons that earthworms are useful in a vegetable garden, they are harmful within our native woodlands that evolved with earthworms. Studies conducted by the University of Minnesota show that at least seven species of earthworms are invading Minnesota’s hardwood forests and causing the loss of tree seedlings, wildflowers, and ferns. Invading earthworms eat the leaves that create the duff layer and are capable of eliminating it completely. Big trees survive, but many young seedlings perish, along with many ferns and wildflowers. In areas heavily infested by earthworms, soil erosion and leaching of nutrients may reduce the productivity of forests and ultimately degrade fish habitat. For more information on invasive earthworms visit the Minnesota Department of Natural Resources web site.

 

 

 

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