1. WHAT DO THESE PLANTS HAVE IN COMMON?
A native wildflower growing in a vegetable garden
A dandelion growing in your lawn
A tomato plant growing in your driveway
Discuss that they are all growing in places most people would not want them to grow. They are “out of place”. If the term “weed” doesn’t come up, ask students if they would consider them weeds. Ask for their definitions of a weed.
Photo Richard Old,
Photo Howard Schwartz, Colorado State University
Photo Joy Viola, Northeastern University

2. WHAT ARE WEEDS?
Weed is a subjective word used to describe any plant growing where it is not wanted, for various reasons.
How might 2 people have different ideas about whether a particular plant is a weed or not?
Discuss the subjective nature of the word “weed” and how its meaning might vary from person to person, depending on perspective.

3. WHAT’S FUNNY HERE?
Ask them to describe what they see. What’s funny about this picture? Why? Where do these plants usually grow?

4. Native (or indigenous) species:
NATIVE PLANTS
Native (or indigenous) species:
Occur “naturally”, or have not been transferred to their location through direct or indirect human actions.
These species have adapted to the environmental conditions of their native range, including the influence of other species, through thousands or millions of years.
Discuss the terms native and indigenous.

5. NON-NATIVE PLANTS
Non-native species (also called alien, exotic, foreign, introduced, or non-indigenous):
Those growing outside of their known native, natural or historic range.
May be from another continent, another part of the same continent, or even from a different part of the same region.
Discuss and then ask students how non-native plants might be introduced.

6. HOW DO THEY GET HERE? Accidentally:
by seeds contaminating animal feed or crop seeds
by seeds hitchhiking on animals, clothing, shoes, vehicle tires, livestock, pets, boats, or other mobile items.
Intentionally:
for ornamental, food, or medicinal value
for livestock forage, windbreaks, or to improve wildlife habitat.
Have they thought of all of these modes of introduction? Have they thought of others not on this list?

7. WHAT’S THE SAME? WHAT’S DIFFERENT?
Ask them what they notice about this large picture. Explain that these are also non-native plants. They differ from the ones in the desert picture they just saw because they are well-adapted to where they are growing, since they lived (evolved) in a similar place, or habitat. Are they considered weeds? Remind them of the definition. It depends on the perspective.

8. NATIVE? NON-NATIVE? WEEDS?
Discuss the differences between non-native plants like knapweed and garden flowers. In one photo, the non-native plants are invasive—they are taking over, or invading, the other vegetation around them and they are identified as invasive plant species by land managers. In the garden photo, they are simply non-native or exotic species which, at least at this time, do not seem to pose any threat to the landscape.

9. HOW DO THEY DO THAT?
Ask what might make a plant invasive. Brainstorm ideas.

10. INVASIVE PLANTS Non-native
Well-adapted to the growing conditions found in their new range.
Freed from the predators, diseases, or close competitors of their native range
Spread rapidly and displace other vegetation
Cause or are likely to cause economic or environmental harm or harm to human health*
* As defined by The National Invasive Species Information Center
Did they think of all of these points?
Now ask what kinds of traits they think might make a plant successful at invading a new area. Make a list.

11. Traits of Successful Invaders
They produce many seeds.
Seeds disperse far and quickly, by being airborne or adhering to fur or clothing.
Seeds may remain viable for many years.
Seeds have high germination rates.
They grow quickly.
They are able to spread vegetatively.
Discuss

12. Traits of Successful Invaders
They have deep roots (leafy spurge roots can reach 20 feet in length!).
They are not palatable to livestock and wildlife.
They are not susceptible to local diseases, parasites, herbivores, etc.
They are allelopathic- they give off chemicals that inhibit the germination or growth of other plants.
Discuss. Now ask if they have heard of the term “noxious weeds”. Can they deduce what it means?

13. NOXIOUS WEEDS
Invasive plants that have been given special designation through a state or federal law.
These laws are designated to protect agricultural production and natural areas by mandating and regulating the control of invasive plants.
Montana has 34 plants on its Noxious Weed list
This is the only one of these terms that has any legal meaning.

14. Noxious weeds have been spreading rapidly in Montana the past 100 years
Over the past 100 years, noxious weeds have been spreading at a rapid rate. For example, spotted knapweed arrived on the west coast in 1893 on the San Juan Islands in Washington. By 1920, this weed had established in over 24 counties in three northwestern states, with several large infestations near Missoula. Now, spotted knapweed has been reported from every county in the western United States and has invaded about five million acres in Montana alone.
Spotted knapweed appeared near Missoula before 1925 and is now in every county in Montana.

15. Montana County Noxious Weed Control Law states:
“It is unlawful for any person to permit any noxious weed to propagate or produce seeds on their land”
How many Noxious Weeds of Montana can you name?
How many Noxious Weeds of Montana can they list?

16. Montana Noxious Weeds:
Canada thistle (Cirsium arvense)
Field bindweed (Convolvulus arvensis)
Whitetop or Hoary cress (Cardaria draba)
Leafy spurge (Euphorbia esula)
Russian knapweed (Centaurea repens)
Spotted knapweed (Centaurea maculosa)
Diffuse knapweed (Centaurea diffusa)
Dalmatian toadflax (Linaria dalmatica)
St. Johnswort (Hypericum perforatum)
Sulfur (Erect) cinquefoil (Potentilla recta)
Common tansy (Tanacetum vulgare)
Oxeye-daisy (Chrysanthemum leucanthemum L.)
Houndstongue (Cynoglossum officinale L.)
Yellow toadflax (Linaria vulgaris)
Hoary alyssum (Berteroa incana)
Purple loosestrife or lythrum (Lythrum salicaria, L. virgatum).
Tansy ragwort (Senecio jacobea L.)
Meadow hawkweed complex (Hieracium spp.)
Orange hawkweed (Hieracium aurantiacum)
Tall buttercup (Ranunculus acris L.)
Tamarisk [Saltcedar] (Tamarix spp.)
Perennial pepperweed (Lepidium latifolium)
Rush skeletonweed (Chondrilla juncea)
Yellowflag iris (Iris pseudacorus)
Blueweed (Echium vulgare)
Yellow starthistle (Centaurea solstitialis)
Common crupina (Crupina vulgaris)
Eurasian watermilfoil (Myriophyllum spicatum)
Dyer’s woad (Isatis tinctoria)
Flowering rush (Butomus umbellatus)
Japanese knotweed complex (Polygonum spp.)
Scotch broom (Cytisus scoparius)
Can your students identify any of these plants? Why might it be important? Besides being legally responsible for controlling noxious weeds, why should they care about invasive plants? Can they think of problems invasive plants might cause? Brainstorm a list.
How many can you identify?

17. WHO CARES? Invasive plants can:
Reduce agricultural production, including livestock forage (more expensive food and less of it for all of us!)
Displace native vegetation, including rare plants
Degrade or eliminate habitat for wildlife
Discuss

18. WHO CARES? Increase soil erosion
Alter the frequency and intensity of fires
Alter hydrologic regimes and degrade water quality and fish habitat
Decrease ecosystem stability by lowering biodiversity and interrupting natural processes
Discuss.

19. HOW DO INVASIVE PLANTS AFFECT YOU?
Can your students think of personal reasons to care about invasive plants?