MATERIALS:
     milkweed plants
     magnifying glass
     milkweed native and non native
     milkweed parts
     milkweed parts worksheet
     tray
     forceps
     Slideshow:  Milkweed Diversity (powerpoint)
 

BACKGROUND:

Native milkweeds (Asclepias spp.) are best known for its larval food for the monarch butterfly.  It also has a unique  flower structure and production of pollin.  The pollen is not the powdery individual grains, but as special packets called “pollinia.”   This pollinia is rich in nectar for the insects, so highly sort after.  The only other major group of plants that have these packets are orchids. 

Milkweed  has distinctive seed pods that produce wind-borne seeds.  The fleshy pods split when mature, releasing the seeds. Milkweed produces a milky substance that is contains latex and complex chemicals that make the plants unpalatable to most animals. When the plant is injured, stems, leaves, and pods ooze this white sap.

There is over 70 milkweed species native to United States and Canada.   The diverse Asclepias genus ranges in habitats from desert to tropical.  Flowers vary in color and fragrance. Many milkweeds are perennial while a few are evergreen.  Milkweeds typically flower in late spring and the end of summer.  Seed dispersal follows the growth cycle.  The perennial species remain dormant through the winter and reemerge in spring from its root system.

The first year the young milkweed builds its roots. Deep sturdy roots that will help it survive drought, floods, and freezing temperatures.

The second year plant is now able to produce a considerable amount of foliage. Adult Monarchs will readily find the plant. Scientists still aren’t certain how monarchs recognize milkweed from the air, but once they land on it, chemical sensors on the feet of the Monarch recognize the milkweed.

Flowers at last! The third year a mature milkweed plant has developed, it produces large lush foliage, ample flowers, and will serve as a nectar source for adult butterflies and bees, and there is plenty of leaves for the caterpillars. After a long-bloom that can last much of the summer, seed pods will form that open in the fall, starting the cycle anew.

PROCEDURE:

Milkweed is a complicated plant and provides habitat for many organisms.  This lab looks into different types of milkweed and looks at the different parts.  This lab is also a way for students to observe, measure and draw.  Ideally it would be good to have 2 different milkweeds, but if the season is not right you may not find two.

PRE:  Cut the milkweed for students.  Include leaves, flowers, seed pods, and stalks prior to lab.

1.  Show the slideshow to students and go over the diversity of plants throughout the world.  Emphasize the parts, especially those they will have to find. 

2.  Use the Milkweed Parts worksheet (which includes the life cycle of milkweed) and go over the different parts. 

3.  Distribute real milkweed.  If you have 2 different milkweeds that would be ideal. Ideal have children look at pods, leaves and stems.

      a.  Make sure they see the "milk" and have a discussion on the texture.  Is it like milk or more viscous.  You may want them to use their senses of smell and touch.  However if you do touch make sure you have a wet paper towel that they can clean their hand.
      b.  Students should take a leaf and see if they can draw the pattern.  Many milkweeds are long and narrow.  If you have two make them draw them side by side.
     c.  Stalk and leaf arrangement.
     d.  Flowers:  arrangement of flowers and individual flower parts
     e.  Seed pod and seeds.

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