This document provides an overview of invasive species for gardeners. It defines invasive species as alien species that cause economic, environmental, or health harm. Invasive species cost Americans $143 billion per year by destroying habitats and outcompeting native plants and animals. The document discusses the biology and management of invasive species and provides examples of common invasive plant species in the region. It recommends actions gardeners can take to prevent the spread of invasives, such as growing native plants, properly disposing of plant materials, and monitoring for new invaders. Resources for more information on invasive species are also listed.

1. Invasive Species 101:
A Primer for Gardeners
Robert Emanuel, Ph.D.
Water Resources and Community Development Faculty,
Tillamook and Clatsop counties

2. Introduction
What are invasive species?
Why should we care?
Biology & management
Some common invaders
What can gardeners do about them?
Resources for more information.

3. Invasive species means an alien species
whose introduction does or is likely to
cause economic or environmental harm
or harm to human health.

6. Biological invaders destroy habitats or
out‐compete native plants and
animals.
Why should we care?
Invasive species costs Americans about
$143 billion/year!
At least 30 new potential biological
invaders enter the US every day…

7. Understanding Biological Invasions

8. Definitions: Invasive Plants
“Weed”
Exotics A plant
(non‐native) growing
where you do
Lots of beneficial
not want it.
species: Crops,
pasture, forestry “Noxious”
& ornamentals.
A regulatory
designation.
“Invasive”
Spreads outside of
Natives cultivation, and
Co‐evolution causes human,
with other environmental,
species, our economic harm.
natural heritage

9. What makes a plant invasive?
Lack normal environmental constraints
Fast growth and reproduction
Highly adaptable a wide range of conditions
Often can transform their environment
Promoted by new or existing disturbances
Less biodiversity in the native ecosystem
Sometimes work with other invasive species

10. Key Stages in Plant Invasions
New Range Limits?
Escape
Adaptation?
Lag Time Invasion
Introduction
Area Infested
Time

11. The Wildfire Model

12. How do we manage invasive plants?
Prevention *
Quarantine before introduction
Monitoring & mapping
Chemical treatment (herbicides)
Biological controls (biocontrol)
Cultural treatment (hand pulling, cutting, etc.)

13. Some Invasive Species

14. Photo ‐ knotweed
Japanese Knotweed: Fallopia cuspidatum

15. Glenn Miller, ODA
Giant Knotweed: Fallopia sachalinese

17. Himalayan Knotweed: Polygonum polystachyum

18. Photo ‐ knotweed
Knotweed: Fallopia x bohemicum

21. knotzillaweed?

22. Photo ‐ English ivy
English Ivy: Hedera helix

23. English Ivy
Photos – black walnut tree covered
2002 by English ivy
2006

24. Policeman’s Helmet: Impatiens gladulifera

26. Garlic Mustard, Alliaria petiolata

28. Parrot feather, Myriophyllum aquaticum

29. Photo: OSU
Yellow Flag Iris: Iris pseudacorus

31. Photo: Wikimedia
Old Man’s Beard: Clematis vitalba

32. Old Man’s Beard: Clematis vitalba

33. Shining Geranium, Geranium lucidum

34. Lynn Ketchum, OSU EESC

35. Photo: University of Georgia
Herb Robert: Geranium robertianum

36. Spurge Laurel: Daphne laureola

38. Photo ‐ butterfly bush infestation in
Lane Co.
Butterfly Bush (Buddleia davidii) Photo: OSU

39. Photo – butterfly bush infestation in
Lane Co.
Butterfly Bush: Buddleja davidii

40. Purple Loosestrife: Lythrum salicaria

41. English Holly: Ilex aquifolium

42. Lynn Ketchum, OSU EESC
Common Gorse: Ulex europaeus

43. French Broom: Genista monspessulana

44. Portuguese Broom: Cytisus striatus

45. Jubata Grass: Cortaderia jubata

46. Fennel: Foeniculum vulgare

48. But wait! There’s MORE!

49. Cotoneaster: Cotoneaster spp.

50. Photo: Kurt W. Heckeroth
Petasites japonica var. giganteum

51. Giant Reed: Arundo donax

52. Photo: University of Georgia
Hydrilla verticillata

53. Photo: Nancy Ness, Grays Harbor, WA; insert: King County
Yellow Archangel: Lamiastrum galeobdolon

54. Orange Hawkweed: Hieracium aurantiacum

55. Capeweed: Arctotheca calendula

56. Ice Plants: Mesembryanthemum,
Lampranthus, Delosperma, Carpobrotus

57. Periwinkle: Vinca major

58. Crimson Fountain Grass: Pennisetum setaceum

59. Tree of Heaven: Ailanthus altissima Photo: USFS

60. Black Locust: Robinia pseudoacacia

61. Orange wisteria: Sesbania punicea

62. Lollipop Tree: Myoporum laetum

63. Salt Cedar: Tamarix ramosissima

64. Only you can prevent the invasion!

65. What can gardeners do?
Know the enemy & teach others about them
Grow native & non‐invasive wherever possible
Help others to do the same
Help the public with information on treatment
Monitor and report new invaders
Check clothes, vehicles, pets when out & about

66. What can gardeners do?
Don’t share unless you know it’s not invasive
Check seed mixes before you buy them
Stay away from generic wildflower mixtures
Watch for hitchhikers in nursery stock
Use weed‐free soil and mulch
Watch introductions for aggressive behavior
Don’t dump your yard clippings in the wild!

67. If you have a known invasive
(but can’t part with it)
Deadhead faithfully
Use root barriers
Dispose of plant material properly—bagged in
the garbage or burned (completely)
Please don’t share your invader with others!
Contain it, control it, or cage it!

68. For Water Gardeners
Always wash new introductions (think snails)
Keep water garden separate from native waters
Never dump water garden materials or water
into native waters
Research your plants for invasive potential—
many commonly used aquatics are!

69. Some Resources

71. http://plants.usda.gov/java/noxiousDriver

75. www.plantright.org

77. Robert M. Emanuel, Ph.D.
Water Resources & Community Development
Tillamook & Clatsop counties
2204 Fourth Street
Tillamook, OR 97141
(503) 842‐5708 X 2
robert.emanuel@oregonstate.edu
blogs.oregonstate.edu/h2onc