4. Invasive Plants What is an invasive plant?
Why are these invasive plants
such a problem?
What are some common invasive plant species across the country?
What we can do to prevent their spread?

5. Definition of Invasive Species
“1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.” an umbrella term referring to alien, exotic, non-indigenous, and non-native species in TWS position paper.
Source: National Invasive Species Council, National Invasive Species Management Plan (
• Definition: Non-native or alien species to the ecosystem under consideration and whose introduction does or is likely to cause economic, environmental harm, or harm to human health.
“Alien species" means, with respect to a particular ecosystem, any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem.

6. How did they get here?

7. Invasive species
Introduced for food, fiber, pharmaceutical ,and ornamental reasons
50,000 invasive plant and animal species are established in the U.S.
5000 plant species have escaped and now exist in U.S. natural ecosystems (Morse et al., 1995)

8. Problems caused by invasive species
Crowd out native plants and wildlife that depend on them.
Disrupt ecosystem processes; hydrology natural succession and pollination
Cause soil erosion and change soil chemistry
Create additional fire hazard

9. Problem of Invasive Species
Invasive plants represent 47% of the total flora of most states. This percentage continues to increase annually (Zheng et al., 2004)
Cost $138 billion annually in the US (Pimental et al., 2000).
USDA’s budget at $990 million.
USACE’s budget at $55 million.
• Approximately 42% of Threatened and Endangered species are at risk because of invasive species (Pimental et al.,2000)

10. Executive Order 13112 Signed by President Clinton, 1999.
Establishes the National Invasive Species Council. Currently there are 13 Departments and Agencies on the Council.
Purpose: to prevent the introduction of invasive species and provide for their control and to minimize the economic, ecological, and human health impacts that invasive species cause
The Council wrote the National Invasive Species Management Plan

11. Definitions
"Control" means, as appropriate, eradicating, suppressing, reducing, or managing invasive species populations, preventing spread of invasive species from areas where they are present, and taking steps such as restoration of native species and habitats to reduce the effects of invasive species and to prevent further invasions.

12. 10 Riparian invasive species
NE Purple Loosestrife; Japanese Stilt Grass
SE Kudzu; Japanese Knotweed
SW Salt Cedar; Giant Reed
NW Cheat grass; Common Reed
Country wide:
Russian Olive; Autumn Olive

13. Invasive Plant Species of Arkansas

14. Purple loosestrife Lythrum salicaria

15. Purple loosestrife Lythrum salicaria
Native to Europe, SE Asia, Russia, India
Listed as a invasive plant in all U.S. states except FL.
Invades and fills habitat niche and provides no wildlife food value
Clogs waterways and sends millions of seeds into water system
Brought here as an ornamental
Change in nutrient cycling of N and alters wetland function (accelerate eutrophication)

16. Japanese Stilt Grass Microstegium vimineum

17. Japanese Stilt Grass Microstegium vimineum
Native to Asia, introduced 1919
Invasive in 15 eastern states
Carpets the Riparian bottomland with thick thatch that prohibits the growth of native plants
It is physiologically adaptive and may alter soil conditions to benefit itself by increasing the pH, nitrification and nitrate

18. Kudzu Pueraria montana Var. lobata

19. Kudzu Pueraria montana var. lobata
Native to China, introduced in late 1876 at the Philadelphia Centennial Exhibition & promoted as a forage crop. Also planted by the CCC to prevent erosion.
Invasive in 22 states
Positive growth response to increasing CO2
Tolerant of nutrient-poor, compacted soils and drought conditions

20. Japanese Knotweed Fallopia japonica

21. Japanese Knotweed Fallopia japonica
Native to Asia, introduced in late 1800’s aws an ornamental plant.
Invasive to 36 states
Grows in Zones 4 – 8, Herbaceous shrub to 3 m tall
Preference for wet environments, riparian and disturbed areas
A synonym for this plant (in some Floras) is Polygonum cuspidatum.

22. Salt Cedar Tamarix ramosissima

23. Salt Cedar Tamarix ramosissima Ledebour
Native to Eurasia and Africa
Small tree, brought in as an ornamental
Noxious weed in 13 western states
Widespread in riparian systems, displacing other native plants.
Water-use rates of Tamarix are among the highest of any phreatophyte evaluated in the S.W. and lowers the water table (can consume 4 ac-ft of groundwater annually).
Increases soil salinity; salts redistributed from deep in the soil to the soil surface which inhibit other plant sp.

24. Salt Cedar Tamarix ramosissima
Control and Management:
• Manual – Digging, root cutting by any
mechanical means, fire and flooding
• Chemical- General use herbicides such as glyphosate or triclopyr; product approved for aquatic application. Follow label and state requirements.
• Biocontrol- 15 insects; a mealybug (Tributina mannipara) and a leaf beetle (Diorhabda elongata) have been released. Leaf Beetle is impacting Endangered Willow Flycatcher habitat. Five other insects are being studied for release in the US.

25. Giant Reed Arundo donax

26. Giant Reed Arundo donax
Native to India and countries around the Mediterranean sea
Forms dense thickets which chokes riverside and stream channels
Crowds out native plants and reduces wildlife habitat
Creates fire hazard
Small plant fragments can travel downstream and invade new areas

27. Giant Reed Arundo donax
Control and Management:
Manual – Repeat mowing is necessary.
Chemical- General use herbicides such as glyphosate. Apply to clumps after flowering. Prescribed burning alone or in combination with use of herbicide. Follow label and state requirements.
Biocontrol agent from Europe being tested.

28. Cheatgrass Bromus tectorum

29. Cheatgrass Bromus tectorum
Native to Europe, N Africa, SW Asia
Invasive in 17 states
Many ecosystems that Cheatgrass has invaded are seriously altered and no longer support the natural plant community and can maintain dominance for many years
Grows in semi arid environment (10”-22” annual precip.)
Long awns can pierce animals feet, mouth, nose, eyes and ears
It is a fuel, creating very hot fires in these grasslands

30. Cheatgrass Bromus tectorum
Control and Management:
Manual – Mowing, grazing, fire and interseeding of competitive native plants
Chemical- General use herbicides such as glyphosate. Follow label and state requirements.
Biocontrol - Pink Snow mold (Fusarium nivale) is being investigated as a control agent.

31. Common Reed Phragmites australis

32. Common Reed Phragmites australis
Native to Europe and the fertile crescent.
Eliminate diverse wetland native plant communities
and provides little wildlife food or shelter
Forms dense monoculture stands quickly and occurs in all 48 continental states.
It can grow in a wide range of soil conditions: in disturbed area, polluted soils, in somewhat dry sites and in water that is 6 feet deep

33. Common Reed Phragmites australis
Control and Management:
Manual – Mowing may be effective.
Burning plant after it flowers in August-September, but fire will stimulate growth in the Spring.
Chemical - General use herbicides such as glyphosate. Follow label and state requirements.
Biocontrol - No known bio-controls at this time.

34. Russian Olive Elaeagnus angustifolius

35. Russian Olive Elaeagnus angustifolius
Native to southern Europe and western Asia
Invasive in 31 states
Interferes with natural plant succession and nutrient cycling and tax water reserves
It is capable of fixing nitrogen and can grow on bare mineral substrate
Birds will eat berries and spread this tree, however ecologists have found that bird richness is actually higher in riparian areas with native vegetation

36. Russian Olive Elaeagnus angustifolius
Control and Management:
Manual – Mowing hedges with brush type equipment and removal of cut material.
Chemical - General use herbicides such as triclopyr or imazapyr. Also Metasulfuron-methyl with a surfactant is also reported to be effective. After manual process will also need to stump treat with herbicide. Follow label and state requirements.
Biocontrol – None known at this time.

37. Autumn Olive Elaeagnus umbellata

38. Autumn Olive Elaeagnus umbellata
Native to Asia, introduced in the 1830’s.
Invasive to 23 states
Shrub or small tree, grows in Zones 4 – 8 and spreads extremely rapidly
Prolific seeding; dispersed by birds and by water. Seed eaten by birds, but not preferentially.
Can live in a wide range of habitats; tolerant of infertile and dry soils. Can alter nutrient cycling

39. Autumn Olive Elaeagnus umbellata
Control and Management:
Manual – Sprouts pulled by hand. Cutting will result in thicker, denser plants. Burning during the dormant season also results in vigorous re-sprouting.
Chemical- General use herbicides such as glyphosate. Foliar application is effective. This is a nonselective herbicide, so care should be taken with other plants. Follow label and state requirements.
Biocontrol – None known at this time.

40. Plantwise Guidelines Know your plants Use non-invasive alternatives
Watch out for invasive plant hitchhikers
Be careful if you share plants
Use only seed mixes that are invasive plant free

41. Plantwise Guidelines Use weed-free soil and mulch mix
Be especially careful with aquatic plants
Keep an eye on new sprouts and volunteers
Dispose of invasive plants carefully
If you can’t part with your invasive plant, remember – contain it, control it or cage it.

42. Sources and websites Plant Management Information System (PMIS)
Plant Management Information System (PMIS)
Aquatic Plant Information System (APIS)
na.fs.fed.us/fhp/invasiveplants/weeds/index.shtm
Huebner C.D Invasive Plants Field and Reference Guide. NA-TP USDA Forest Service.
Invasive Plants of the Eastern United States Identification and control
(for invasive sp.list serve)

43. Review
Definition of invasive species: Non-native or alien species to the ecosystem under consideration and whose introduction does or is likely to cause economic, environmental harm, or harm to human health.
Invasive plants are a problem because they crowd out native species, do not support our native fauna, cause native species to become threatened and endangered, alter the soil chemistry, alter hydrology and present a fire danger.

44. Review 10 Riparian invasive species
NE Purple Loosestrife; Japanese Stilt Grass
SE Kudzu; Japanese Knotweed
SW Salt Cedar; Giant Reed
NW Cheat grass; Common Reed
Country wide:
Russian Olive; Autumn Olive

45. Contact information