National Agricultural Literacy Curriculum Matrix
Walnuts: The Importance of Grafting
3 - 5
The purpose of this unit is for students to understand the science and economic importance of grafting walnut trees.
For each student
- Let's Graft! student worksheet
For each partnership of 3-4 students:
- two colors of play-doh plastic knife
- 6 oz. plastic cup
- sand or soil
- white paint
- paint brush
- rubber band
Essential Files (maps, charts, pictures, or documents)
- Walnut Grafting Crossword & Answer Key (optional)
- Lets Graft! student worksheet
- Answer Key- Let's Graft
fluctuate: to shift back and forth unpredictably
fuse: to become blended or joined
graft: to insert a twig or bud from one plant into another plant so that they are joined and grow together
indigenous: native, or original
propagate: to grow, generate, or produce
rootstock: a root or part of a root to which an aboveground plant part is grafted
Did you know? (Ag Facts)
- Walnuts are the oldest known food from a tree dating back to 10,000 BC.1
- There are more than 30 varieties of walnuts.1
- Walnuts have Omega-3 fatty acids, magnesium, and vitamin E. They are a healthy treat.2
Background Agricultural Connections
Interest Approach – Engagement
- Introduce the walnut to the students. Show them either a picture or an actual walnut both inside and outside of the shell.
- Ask, "Where are these produced?" (they grow on a tree.)
- Show the Walnut Harvest and Processing video produced by the California Walnut Board.
- Distribute worksheet, Let’s Graft! to students and read together the informational paragraphs before beginning the activity.
- Divide students into groups of 2-3 students per group and distribute materials for the activity. Make sure each student will have enough play-doh for 5” long ropes.
- Explain to students that they will be simulating how grafting is done.
- Ask students to roll each piece of modeling clay or play-doh separately into ropes that are approximately one inch in diameter throughout.
- As students are working, ask them to compare their rolled piece of clay with their lab partner’s. Ask them to continue working until they feel the diameter of each rolled piece of clay is the same.
- Assign each colored piece of clay as the scion or rootstock to help students differentiate between the two pieces that are grafted together.
- Using the plastic knife, have students cut a diagonal cut that measures approximately one inch from one end of one of the ropes and leave the other end untouched. This piece of clay is the rootstock.
- Ask the students to set the piece of clay down once the appropriate cut has been made.
- Have students pick up the other piece of clay and make a similar one-inch diagonal cut on one of the ends. On the other side of the rope, ask students to cut the clay so it is a straight cut. This piece of clay is the scion.
- Using the plastic knife, ask students to cut a small notch on both pieces of clay in the middle of the diagonal cut.
- Place the ropes of clay end to end with the diagonal cuts and notches connecting together as shown in the diagram.
- Cut one end of a rubber band. Holding both ends of the rubber band, carefully place the middle of the rubber band in the middle of the graft. Tell students to think of the rubber band like a bandage.
- Carefully wrap the rubber band around the graft and tie the ends together in a knot.
- Tell students that farmers paint the rootstock white to protect it from the sun. Ask students to paint their rootstock white.
- Share with students that farmers dip the top of the scion in wax to keep it from getting dried out. Using the wax from a melted candle, have students coat the top part of the scion with wax.
- Place sand or soil into a plastic cup. Gently “plant” the grafted walnut seedling making sure to bury only the bottom of the rootstock.
Concept Elaboration and Evaluation:
After conducting these activities, review and summarize the following key concepts:
- Technology and science is used to improve the production of farm products. Walnuts are an example.
- Scientists and farmers study inherited traits in walnut trees in order to produce the best walnuts.
- Walnuts are grown on trees.
- California produces the majority of all walnuts produced in the United States.
Take the students on a field trip to a walnut orchard nursery. Ask a horticulturist to share with students how walnut seedlings are grafted. Have students make observations of the walnut tree’s truck. Can they see where the grafting took place? What do they notice? Compare the size of the young trees with the older trees.
Have a walnut farmer visit the classroom and share his work on the farm.
As a class, plant a walnut seed and see how long it takes to germinate. Offer students a prompt about the growth of the seed and ask them to write a creative story about what will happen to the seed when it sprouts.
Obtain different species of walnuts (California Black walnut tree, Juglans californica and English walnut, Juglans regia). Have students compare and contrast the physical difference of each species.
Demonstrate the importance of matching diameters of the scion and rootstock when grafting using a celery stalk. Trim the bottom of a celery stalk keeping the leaves intact and place it is a clear cup filled half full of water adding 8 drops of red food coloring until the water is a deep red color. The next day the leaves of the celery will be red. The water and nutrients are carried up through the celery stalk by the xylem. The xylem is the woody tissue in plants that is responsible for the movement of water and nutrients throughout the plant. During the grafting process, it is important to match the woody part of the walnut cuttings so the xylem and phloem (food conducting tissue) have the best possible chance of growing together. This will increase the likelihood of the walnut tree’s success.
Place a stock of freshly cut celery in colored water. Have students observe the changes in color of the celery the next day. Explain to students that plants need water to survive and they draw water up from their roots through their capillaries. The capillaries are hollow and act a lot like a straw. Share with students this is why when grafting it is important to match the diameter of the rootstock with the scion.
Suggested Companion Resources
- The Tree Farmer (Book)
Agricultural Literacy Outcomes
Food, Health, and Lifestyle
- Diagram the path of production for a processed product, from farm to table (T3.3-5.b)
Science, Technology, Engineering & Math
- Describe how technology helps farmers/ranchers increase their outputs (crop and livestock yields) with fewer inputs (less water, fertilizer, and land) while using the same amount of space (T4.3-5.b)
- Identify examples of how the knowledge of inherited traits is applied to farmed plants and animals in order to meet specific objectives (i.e., increased yields, better nutrition, etc.) (T4.3-5.c)
- Provide examples of science being applied in farming for food, clothing, and shelter products (T4.3-5.d)
Education Content Standards
5-LS1: From Molecules to Organisms: Structures and Processes
5-LS1-1Support an argument that plants get the materials they need for growth chiefly from air and water.
Common Core Connections
Reading: Anchor Standards
CCSS.ELA-LITERACY.CCRA.R.1Read closely to determine what the text says explicitly and to make logical inferences from it; cite specific textual evidence when writing or speaking to support conclusions drawn from the text.
CCSS.ELA-LITERACY.CCRA.R.7Integrate and evaluate content presented in diverse media and formats, including visually and quantitatively, as well as in words.
Writing: Anchor Standards
CCSS.ELA-LITERACY.CCRA.W.1Write arguments to support claims in an analysis of substantive topics or texts using valid reasoning and relevant and sufficient evidence.
CCSS.ELA-LITERACY.CCRA.W.2Write informative/explanatory texts to examine and convey complex ideas and information clearly and accurately through the effective selection, organization, and analysis of content.
CCSS.ELA-LITERACY.CCRA.W.5Develop and strengthen writing as needed by planning, revising, editing, rewriting, or trying a new approach.
CCSS.ELA-LITERACY.CCRA.W.9Draw evidence from literary or informational texts to support analysis, reflection, and research.