Aztec Floating Gardens

Vanessa Villalobos             Oscar Mayer Elementary
                               2250 N. Clifton 
                               Chicago IL 60614
                               (312) 534-5535

Objectives:

     This lesson was created for students of all ages at the elementary level 
grades K-8.  Students will be participating in a series of short experiments 
involving plants in order to discover ways to create a hydroponic garden.  
Aztec history will be explored to gain student interest and to set up the 
background for the analysis and creation of the "Floating Gardens".

Background Information:

     The basis of this project is phenomena derived from Aztec history.  
The Aztec civilization thrived for three centuries and successfully grew a 
multitude of produce including pumpkin, squash, and corn.  The amazing aspect is 
that their crops were underwater due to the fact that where they were located, 
Tenochtitlan (now known as Mexico City), was primarily wet, marshy land.  In 
order to survive, the Aztecs had to create ingenious ways of producing crops in 
underwater conditions.  The students, like the Aztecs, will be faced with the 
problem of recreating an underwater garden in the classroom. 

Materials Needed:

     -celery stalks (8 to 10 depending on class or group size)
     -red or blue food coloring
     -clear plastic cups
     -1 lb bag of sand
     -1 lb bag of potting soil
     -seeds of various plants i.e. peas, Mexican sunflowers, beans, etc.
     -ziploc baggies
     -paper towels
     -large, clear plastic containers (garden itself)
     -10 carrot tops (sliced from carrots)
     -10 sponges (artificial or real, although real will work best)
     -white carnations (optional)
     -steel or plastic mesh
     -large square or rectangular tupperware containers

                                Time Constraints:

     This unit, depending on class setup, will require one to six weeks.

Procedure:

                               Mini-experiment #1:

     This first "mini-experiment" will introduce the concept of how plants 
acquire nutrients from the stem upward.

1.  Add 8-10 drops of red or blue food coloring to water in a clear cup.
2.  Place a celery stalk or white carnation inside the cup.

     Within 20 minutes, students will observe that the dyed water has been 
transported upward within the stem and has been deposited at the leaf tips.  If 
possible, have the students observe a cross-section of the celery (or flower) 
under a microscope and label all parts.  The next day, the changes will be even 
more dramatic, the leaves having a vibrant, dyed color. 

                               Mini-experiment #2:

     This mini-experiment will dispel a common idea among students; that only 
the method of growing plants is with black soil and seeds.

1.  In a small circular pan (the black bottoms of 2 liter bottles will also 
    suffice) add 2 inches of sand.
2.  Cut the tops off of several carrots and place them in the pan with sand.
3.  Add a small amount of water to the pan, enough to make the sand damp.

     Within a few days, the students will observe the carrots beginning to 
sprout.  The carrot tops contain the necessary elements to grow into another 
carrot plant and can be transported at another time.

                               Mini-experiment #3:

     This experiment will build upon the previous activities' concepts and 
continue to establish that plants can grow in various environments.

1.  Soak a variety of beans in a pot for one evening (if this step is not 
    completed, the seedlings will sprout, but will take a longer time).
2.  Fold a paper towel into fourths and add enough water to dampen the 
    towel throughout.  Place the towel inside a ziploc baggie.
3.  Place 8-10 beans inside the baggie on top of the folded towel.
4.  Tape the baggies to the window.

     In a few days, the students will observe many changes and should take 
detailed notes.  Discuss the idea that inside each seedling lies "a baby plant"
waiting to grow.

                               Mini-experiment #4:

     The students should now be knowledgeable and ready to create their floating 
gardens.  Working in groups, the students should make a list of materials needed 
for their gardens and then set out to obtain those materials on their own.  
However, depending on the age level, this may not be possible.  In any case, the 
students may need a variety of materials with which to begin.  Soil, sand, 
plastic containers, seeds, and plastic or wire mesh are the staples of this 
experiment.  Allow the students to work with their groups to discuss and draw 
up plans for their gardens using previous experience and research. 

1.  Take the large, plastic tupperware containers (or similar containers), and 
    have the students fill them almost completely with water.
2.  Using different materials, the students should now construct their floating 
    gardens based on the group's plans, ideas, and drawings.

     It will be interesting to see the different combinations the students have 
created.  Some will create gardens with sand bottoms, soil bottoms, or a mix of 
both.  Other groups may make multi-level gardens with irrigation systems.

Performance Assessment:

     Once the students have completed their gardens, they should present 
them to the class.  Students are to explain how they built their gardens and why 
they think their gardens will enable plants to grow.  Questions can then be 
presented to the groups to guide discussions and provide constructive criticism.
Each student should then keep detailed notes of all activities and changes that 
occur within the gardens.