Keywords: growth rings, cookie, sapwood, cambium, outer bark, heartwood, pith; Lesson Plan Grade Level: ninth through twelfth grade; Total Time Required for Lesson: 30 minutes of explanation and examples, teacher can decide on length of time to give students to research topic, one week from date of assignment given; Setting: an area where they can research historical events, computer lab works great for this lesson but sometimes makes the lesson easier for the students to complete because they can find a time line that can be cut and pasted.

Goals for the Lesson

  • Identify the parts of the inner tree from the bark to the pith of the tree.
  • Develop a topic of student interest to find a historical event for each growth ring.
  • Design a time line.
  • Gain knowledge on how to research topics by means of reference books and computer search engines.

Materials Needed

  • cookie or a cross section of a tree that shows the growth rings. It is nice if the bark is intact but not necessary.
  • small finishing nails
  • masking tape
  • markers or pens
  • poster board or construction paper
  • hammer

State Standards Addressed: Renewable and Nonrenewable Resources (4.2); Agriculture and Society (4.4); and Ecosystems and Interactions (4.6)

Subjects Covered: tree biology, history

Topics: forest history, plant science, plant functions


Part 1: Lecture

The first part of the lecture should be spent on identifying the parts of a cookie or tree round. Define and explain the function of the following

  • outer bark
  • cambium layer
  • sapwood
  • heartwood
  • pith (center of the tree.)

Part 2

Explain to the students how to count growth rings of a tree: count the number of darker rings from the center all the way out to the bark of the tree. Explain to the students that each ring represents one year's growth and this is one way of dating how old a tree is or how old a stump is in the forest. Make sure the students realize that the center of the tree is the oldest part and the outer most rings are the newest growth.

When you start to determine the age of the tree I have my students use masking tape and nails. I have the students write the current year on the tape and wrap it around a nail head. They then put the nail in the growth ring closest to the bark. Next they need to do the same for each ring in the tree back to the pith of the tree. Note: Plan ahead when giving the students a cookie. Choose a cookie that has about the number of years you want them to research latter. Remember if you pick a hundred year old tree they will have to find an event that happened in each year.

Part 3

On a piece of paper or poster board have them neatly write out the number of years the tree is old by date. Example: 2002, 2001, 2000, 1999 back to the year found in the center.

  • Example 1: Have the students pick a particular topic such as cars, birthdays, show tunes, music, championship teams, etc. This is now what the student needs to research. If the students pick cars they need to find one kind of car that came out in each year; if they pick birthdays they need to find one famous person that was born in that year and so on. On their poster board they can use pictures or write them out. Encourage the students to be clever and unique about their display.
  • Example 2: Students have to find one historical event that happened in each year. Beware, students can find completed time lines and just print them out and use as their display unless you state before hand that this will not be accepted.


A collected poster board or paper detailing the events that occurred in the correct years as well as a cookie with the growth rings completed correctly. A follow-up quiz can also be given to make sure the students can identify the parts of a cookie from pith to bark.


"In conclusion, I hope that you can see that the tree that has been cut down has lived through history just like you have. The tree is a representation of decades of change."


Herren, Ray (2002). The Science of Agriculture: A Biological Approach . Independence, Ky.: Delmar Publishing.


Andrew Boyer, Northern Tioga School District