Lesson Plan Title: Invasive Plant Seed Dispersal

Grade Level: 3-8

Concept / Topic To Teach: Identify how common invasive Wyoming weeds are dispersed

Specific Objectives:

Students will describe four ways that plants disperse seeds

Students will explain why plants disperse seeds

Students will analyze invasive plant species at Welch Ranch and identify how each species disperses its seeds

Students will create a plan to control the spread of invasive plant species at Welch Ranch

Required Materials: Background information on seed dispersal for each student, Invasive plant species identification cards, Seed dispersal recording sheet, clipboards, pencils, chart paper, markers

Anticipatory Set (Lead-In):

  1. In the classroom, have students read and discuss background information on seed dispersal. You may want to show students pictures of plants that disperse seeds each of the four methods. Ask students to brainstorm some plant strategies to accomplish seed dispersal.
  2. Explain to students that the site they’re on today has a variety of invasive plant species that the BLM is trying to control. An invasive plant is one that did not evolve in the area and causes significant economic and/or ecological impacts. Have students read background information on invasive plant species and then discuss. Ask students if they have a flower bed or garden at home. Does it get weeds? What is a weed? Is it similar to an invasive plant?

Step-By-Step Procedures:

  1. Explain to students that today they will get a chance to study a variety of invasive plant species on site and analyze the plants to decide which dispersal method is used by each.
  2. Divide students into groups of two or three. Each group should have a seed dispersal recording sheet, clipboard, pencil, and a set of invasive species identification cards.
  3. Discuss how scientists classify plants. Students could come up with their own classification system to aid them as well. Groups should use identification cards to find invasive plant species on site. On recording sheet they should record each invasive plant species found, dispersal method they think the plant is using, and their reasoning behind their analysis. Depending on the season, it might be difficult to tell on some plants. Identification cards (using pictures) or research done when back at school may be beneficial in some cases.
  4. Once groups have finished up, compare results. Did groups agree on dispersal methods for each plant? If there were discrepancies, explain why these occurred. Ask students to explain how seed dispersal affects the spread of invasive plant species. What can the community do to help stop the spread of these weeds? Why is it important to stop the spread?

Closure (Reflect Anticipatory Set):

As a class, have students come up with a plan for how the community can take action to stop the spread of invasive plant species on Welch Ranch. Record the plan on chart paper. Challenge students to share information with family, friends, and community members. Class could write a letter to the school or local town council sharing the information.

Assessment Based On Objectives:

Were students able to correctly identify invasive weed species and seed dispersal methods? Were they able to come up with a sensible plan to control the spread of these weeds?

Invasive Plant Species / Dispersal Method / Reasoning
Ex: Dandelion / Wind / Parachute-like hairs attached to seeds, easily detach and float in wind

Plant Seed Dispersal Methods

In order for the next generation of plants and trees to flourish, a parent plant tries disperse its seeds far from itself to decrease competition between itself and the future seedlings. The seedling will compete with its parent plant for basic needs such as sunlight and water if dispersed too close. Plants have solved this problem through a number of interesting adaptations. These adaptions include dispersal by animals, wind, water, and explosions. Look closely at some plants. Can you tell how they were dispersed?

Plants can’t move, but they do have ways of scattering seeds as far from the parent as possible. Some seeds may even end up more than a hundred miles away from the parent tree. One way is through animal dispersal. Seeds may stick to the fur of an animal and be dispersed that way. The seeds may also be covered in a tasty fruit that the animal eats and then disposes of later in its fecal matter.

Another dispersal method is the use water. Catkins hold tiny seeds that can float in water and are dispersed downstream. Some plants can travel thousands of kilometers across vast bodies of water. Water lilies are another example of a plant that uses water for dispersal purposes.

Wind is a third dispersal method that plants may rely on. Trees like the maple and linden have seeds with wings and rely on the power of the wind to carry the seeds away from the parent. Seeds can be carried a significant distance.

The final dispersal method that plants may use is dispersal through explosion. Pods will dry and split open suddenly thrusting the seeds out with considerable force. The seeds are cast out a considerable distance from the parent plant.

Invasive Plant Species

Invasive plant species have a variety of unique adaptations that help them survive along with a lack of natural enemies. These unique adaptations include:

  1. Great efficiency when it comes to converting the sun’s energy into plant growth
  2. Many plants can establish new plans from both seeds and roots
  3. Seeds can remain viable for over 50 years
  4. Deep and extensive root systems hold large food reserves
  5. Have the ability to produce biological toxins and change soil chemistry which prevents the establishment of other plants
  6. Seeds spread easily
  7. Plants can withstand extreme environmental conditions such as droughts and floods

These adaptations give them a competitive edge over native plants and result in devastating economic and ecological impacts. They affect forage for livestock and wildlife, crops are negatively impacted, and the recreation value of sites decreases. Some invasive plant species, such as cheatgrass, are more vulnerable to fires. In addition, entire ecosystems are damaged.

References

Bureau of Land Management. (2014). Some common invasive plants in Wyoming. Retrieved from

Oregon Natural Resources Education Program.(n.d.).Invasives: plants on the move. Retrieved from