Grow a Weed, Kill a Weed Lab
Due Date______ Period______Name_____________________________________
Observation/Problem: The State of Montana has designated many weeds as noxious weeds.
These weeds cause wide spread economic damage to ranchers, farmers, wildlife habitat, and native plant populations. Using the mtwow.org web site, list the common and scientific names of the category 1, 2, and 3 weeds in MT.:
Be sure and write the sci. names correctly!!
Question: What is a weed?:
Now you will receive some weed seeds from your instructor. Plant them as instructed, read the literature provided about your weed and sum this up in your data notes.
Common and scientific name of my weed:
Draw your weed seed and describe what about it might help this plant disperse (spread) its seeds:
1. After having planted the weed seed(s) as instructed and read the information about your weed, you must care for the weed every class day (water if needed, check health, and turn the pot if the light comes from the side). Record the date of each observation in your notebook!
2. When the weed sprouts, record the date and then sketch and describe its growth once each day.
3. After the first week of growth you will only take data on your weed once a week. You will: 1) Sketch the plant, 2) measure the height of the longest stem, 3) count the number of stems, and 4) note big changes.
4. Water, fertilize (if needed) and repot the plant as instructed. Be sure and keep the soil moist but not soggy
5. When the plant flowers, draw the flower and label the following parts: stem, sepals (these may fall off on some flowers when they bloom), pistil, anthers, and petals. If your plant does not flower by the end of the lab, draw another students flower. Refer to the standard flower drawing in your text.
6. When several flowers of the group have matured, observe and draw the pollen. To do this, rub the anthers in a drop or two of water on a microscope slide, place a cover slip on the slide and observe on 4X, 10X and 40X. Draw your 4X and 40 X views.
WARNING: do not let seeds from your noxious weed escape! We must prevent their spread!!
7. At the end of this lab you will attempt to kill your weed (they may be harder to kill than you think!). Each person will try a different weed control method. List each classmates name and method in your data. Some suggested methods are: 1) apply a herbicide, 2) simulate a wildfire - burn the stems and leaves, 3) defoliate the plant the way a leaf feeding biological control agent might, 4) let a goat or sheep eat the stems and leaves - a cultural control method, 5) dig up the plant, chop it up and rebury the parts - to simulate plowing/tilling, 6) etc.. Do these carefully with teacher supervision! Now water the remains of your plant for 2 more weeks and see if your method really works to kill the plant.
IMPORTANT WARNING: Dispose of the plant parts and soil as instructed in a manner that prevents the spread of these noxious weeds (disposal in a land fill is one suggestion).
8. Complete the results, discussion and conclusion.
Results: In a few sentences, sum your data.
Discussion: Answer these Discussion Items on your own paper.
1. Explain why plants have seeds and fruits with several examples of each.
2. What is a weed? Why are many plants weeds?
3. Why are specific noxious weeds in Montana classed as category 1, 2 & 3?
4. a. Describe how your weed grew (its life stages). b. Make a line graph of the growth of your weed.
5. Describe the function of each part of your flower (stem, sepals, pistil, anthers, petals and pollen).
6. Explain: 1) chemical, 2) biological, and 3) cultural weed control.
7. What is the idea of Integrated Pest (Weed) Management [IPM]?
8. How can you (yourself!) help: 1) prevent weed spread, and 2) help control weeds already established in your area? Explain several examples of each!
Conclusion: a minimum of 3 sentences of summary and 3 sentences of your opinion about the lab.
Teachers: Feel free to copy and past this text into your favorite word processing program and modify it as you see fit!
These instructions assume a teacher with a basic biology background and some knowledge of growing plants.
Materials: weed seeds (you or a weed fighter must collect these), safe seed container, grow lights or greenhouse, growing area, pots (many weeds are tap rooted and need deep pots), potting soil or soil, water, rulers, student data notebooks, graph paper, flower and noxious weed literature, Internet access, microscopes, slides, cover slips, lens paper, forceps, stereo scopes and/or hand lenses, various materials to "kill the weed."
Teacher Instructions: This can be a full year or a half year lab. Select and gather weed seeds from noxious weeds in your area before school starts (some species such as spotted knapweed can be gathered after school starts as the seeds stay in the seed heads). Be careful to prevent weed spread!! You may want the whole class to try all one species, or try several. Try small groups or individual students (fit this to the needs of your students!). Contact your County Weed Coordinator and/or Extension Agent for more information (have them speak to your class / you may be surprised how helpful they will be!!). Educate yourself about the weeds of your area! Try growing the species of your choice at least once (or with a small group of students) so you know what to expect when you do the lab with a whole class.
Start with an introduction to noxious weeds (use a weed fighter speaker, the Internet, a slide show and/or a local rancher/farmer!) and then go over the whole lab with the students. Give them the reading material about their weed. Get the weed literature from the Internet and/or your local weed fighters (The Federal and State agencies will also have "free stuff").
Sprouting Seeds: Each weed seed has different needs, research this yourself. To keep costs down, we usually use local soil (free-dug up from the waste areas of the school grounds) for the bottom 3/4 of the pot and sterile potting soil (we purchase large bags from a local greenhouse) for the top 1/4th. This potting soil suppresses the unwanted seeds (sprouts from the local soil (seed bank) can not push up that high) and helps sprouting success. Many weed seeds need to be planted quite shallow, misted and the pot covered with a clear plastic wrap cover ‘till the new sprout is well established. The students can also sprout them in smaller pots (such as plastic cups or yogurt cups) and transplant the best plant at a later date.
Growing the Weed: Make sure the plants have a normal growing environment with constant warmth, grow lights and/or sunlight, water and room to grow (some weeds get quite large!). Unless soil is reused, fertilizer is not usually needed.
Flower Observation: Teach about the structure and function of flowers before this so the students know what to look for. Have drawings or models of flowers for them to refer to and print off some pictures of their actual weed species flowers to help explain the evolutionary modifications that have occurred with each particular species.
Pollen Observation: Make sure the students have used microscopes, slides and cover slips and have observed samples on all powers before you attempt this part. They can either cut off the anthers or just rub the whole flower in the drop of water on the slide. You may want to get other flowers (from your local floral shop, greenhouse or outside in season) to show the variety of pollen.
Kill the Weed: Make sure you have CONTROL of this part of student activity!! Herbicides (plant growth hormones), burning, chopping, etc. are dangerous and must be treated accordingly!! Keep weeds from spreading!! Have the students simulate many of the ways that weeds are controlled (get suggestions from your local weed fighters.
Disposal and Clean Up: These are noxious weeds and must not be spread. We double bag the soil and transport it directly to the land fill for burial. We wash the pots in indoor sinks and sterilize them. Wash and sterilize your growing area. Monitor the (your) area for potential weed sprouts for 10 years! Inform the local weed fighters of this activity!! Be thoughtful and careful....
Goals: Feel free to copy and paste these into your lesson plans and modify as you see fit.
(-) = "The students will..."
-understand the concept of a noxious weed and be familiar with the Montana category 1, 2, and 3 noxious weeds.
-correctly write genus and species names (scientific names).
-sum literature about the growth habits of one particular weed of our area.
-draw and describe a seed.
-describe how seeds and fruits help with seed dispersal.
-sprout seeds and grow a plant.
-record data over a long period of time and use these data to make a graph.
-draw and describe the structure and function of a flower and its parts.
-use a microscope to observe pollen.
-simulate a weed control method.
-understand and explain why noxious weeds are an ecological and economic problem.
-be able to explain chemical, cultural and biological weed control methods.
-identify at least one weed species in the field.
-understand various ways to prevent weed dispersal.
-understand the idea of IPM.
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