Invasive Plants

Of the 980 species of vascular plants found in the Crab Orchard National Wildlife Refuge (CONWR), about 190 are considered "alien", that is, introduced from somewhere outside the region and propagating. Among these plants are some whose introduction causes economic or environmental damage and even direct harm to human health. These species are called invasive. Exactly how one defines "damage" or "harm" can be debated, but generally biologists refer to changes in the landscape that result in the loss of biodiversity. Many aliens are now considered "naturalized", that is they have been incorporated into the flora but have not displaced native species (to a great extent) or caused economic harm. Examples of these include dandelion (Taraxacum officinale), Heal-all (Prunella vulgaris), and sweet flag (Acorus calamus). The full list of alien and invasive species for the CONWR can be obtained here (Excel file).

Exactly why the invasive species is able to out-compete native species is still not fully understood, however, it is clear in some cases that the nonnative species does not experience the same selective environment, particularly from herbivorous insects. Have you ever wondered why the leaves of your Bradford pear tree are nearly intact at the end of the growing season whereas native trees show lots of evidence of feeding? An excellent book that gives ample examples of this phenomenon is Bringing Nature Home (2007) by Douglas Tallamy who also provides justification for planting native plants. Another excellent book is Invasive Plants by Sylvan R. Kaufman and Wallace Kaufman (2012) which is a guide to identification of North American invasive plants as well as information about their impacts and control.

For the state of Illinois, the following are valuable references:

• Osborne, T. and B. Steffen. Invasive plants of southern Illinois. River to River Cooperative Weed Management Area. Published by the Illinois Natural History Survey, Institute of Natural Resource Sustainability. (pdf file)

• Gage, K. 2014. Management of invasive plants of southern Illinois. River to River Cooperative Weed Management Area. (pdf)

• Gage, K., T. Bethke, and C. Evans. 2017. Management of invasive plants and pests of Illinois.

• Invasive Plant Atlas of the United States. Website developed by University of Georgia - Center for Invasive Species and Ecosystem Health in cooperation with other organizations.

From the list of alien species present on the CONWR, we have selected 40 that meet the criteria outlined above as being invasive (thanks to Chris Evans for input!). This list should be considered a "work in progress" that is likely to change in the future. New alien species are constantly being introduced into southern Illinois (mainly because of human activities), but only some of these advance to invasive status. The species are arranged first by eudicot/monocot and then alphabetical by family and species. Click on the thumbnail images to see more photos (the link takes you to PhytoImages).

EUDICOTS
Achyranthes japonica (Amaranthaceae) Japanese Chaff Flower. Introduced (Asia). Fact Sheet on ecology and control of this species.
	Conium maculatum (Apiaceae) Poison Hemlock. Introduced (Europe)
Pastinaca sativa (Apiaceae) A few large, dense patches of this occur on the refuge. (Apiaceae) Wild Parsnip. Introduced (Europe)
	Hedera helix (Araliaceae) English Ivy. Introduced (Europe)
Carduus nutans (Asteraceae) Musk / Nodding Thistle. Introduced (Europe)
	Berberis thunbergii (Berberidaceae) Japanese Barberry. Very problematic throughout Illinois, present on the refuge, thus it is a priority species  Introduced (Asia)
Alliaria petiolata (Brassicaceae) Garlic Mustard. Introduced (Europe)
	Lonicera japonica (Caprifoliaceae) Japanese Honeysuckle. Introduced (Asia)
Lonicera maackii (Caprifoliaceae) Amur (Bush) Honeysuckle. Introduced (Asia)
	Celastrus orbiculatus (Celastraceae) Oriental (Round-leaved) Bittersweet. Introduced (Asia)
Euonymus alatus (Celastraceae) Found on refuge in several locations; a high priority species (Celastraceae) Winged burning bush. Introduced (Asia)
	Euonymus fortunei (Celastraceae) Wintercreeper, Climbing Euonymus. Introduced (Asia)
Dipsacus fullonum (Dipsacaceae) Common Teasel. Introduced (Europe)
	Dipsacus laciniatus (Dipsacaceae) Not as common as common teasel but still found on refuge (Dipsacaceae) Cutleaf teasel. Introduced (Europe)
Elaeagnus umbellata (Elaeagnaceae) Autumn Olive. Introduced (Eurasia)
	Lespedeza bicolor (Fabaceae) Several large stands of this occur on the refuge. (Fabaceae) Shrub Lespedeza. Introduced (Asia)
Lespedeza cuneata (Fabaceae) Sericea Lespedeza, Chinese Bush-Clover. Introduced (Asia)
	Melilotus albus (Fabaceae) Known for being problematic in open areas in southern Illinois. Seen in young prairie plantings on the refuge. (Fabaceae) White Sweet Clover. Introduced (Eurasia)
Melilotus officinalis (Fabaceae) Known for being problematic in open areas in southern Illinois. Seen in young prairie plantings on the refuge. (Fabaceae) Yellow Sweet Clover. Introduced (Europe)
	Pueraria montana (Fabaceae) Kudzu-vine. Introduced (Asia)
Securigera varia (Fabaceae) Crown Vetch. Introduced (Europe)
	Myriophyllum spicatum (Haloragaceae) Amazon Water Milfoil. Introduced (tropics)
Perilla frutescens (Lamiaceae) Beefsteak Plant. Introduced (Asia)
	Lythrum salicaria (Lythraceae) Purple Loosestrife. Introduced (Europe)
Fatoua villosa (Moraceae) Apparently spreading rapidly (Moraceae) Mulberry Weed, Hairy Crabweed. Introduced (Europe)
	Morus alba (Moraceae) White Mulberry. Introduced (Asia)
Ligustrum vulgare (Oleaceae) Common (European) Privet. Introduced (Europe)
	Clematis terniflora (Ranunculaceae) Yam-leaved Clematis. Introduced (Asia)
Rosa multiflora (Rosaceae) Multiflora Rose. Introduced (Asia)
	Pyrus calleryana (Rosaceae) Spreading rapidly across the state and is a common invader of tree plantings and open areas on the refuge (Roseaceae) Callery pear. Introduced (Asia)
Ailanthus altissima (Simaroubaceae) Tree-of-Heaven. Introduced (Asia)
MONOCOTS
	Dioscorea polystachya (Dioscoreaceae) Chinese Yam. Big stands of this species occur on the refuge.  Problematic invader. Introduced (Asia)
Hemerocallis fulva (Hemerocallidaceae) Orange Day-Lily. Introduced (Eurasia)
	Egeria densa (Hydrocharitaceae) Giant / Brazilian Waterweed. Introduced (South America)
Najas minor (Najadaceae) Eutrophic Water-Nymph. Introduced (Eurasia)
	Bromus tectorum (Poaceae) Downy Cheat Grass. Introduced (Europe)
Microstegium vimineum (Poaceae) Stilt Grass, Japanese stiltgrass. Introduced (Asia). Field guide to identification of this species.
	Phragmites australis (Poaceae) Reed. Native and Introduced (Native to Old World)
Sorghum halepense (Poaceae) Johnsongrass. Introduced (Eurasia)
	Potamogeton crispus (Potamogetonaceae) Curly Pondweed. Introduced (Europe)