Investigating Trees: Using a dichotomous key to identify local tree types

Suzanne Bot, Kimberly Lane Elementary School, Plymouth, MN
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In this set of activities, students identify the types of trees that are in their schoolyard and around their neighborhoods. Students are encouraged to use inquiry methods to develop their own systems of classifying the trees. They are expected to present their classification to others. Students will also be using dichotomous tree identification keys to further explore typical methods of tree classification. Students will be able to compare their own system of classification to what they see in the dichotomous key.

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Learning Goals

  1. Students will learn that trees can be identified by their leaves/needles.
  2. Students will use leaves to determine the types of trees in their community.
  3. Student will present their findings about trees to their classmates.
  4. Students will compare their findings to other areas of the state, country and world.

Context for Use

This activity is designed for students to use a variety of skills including classifying, critical thinking and inquiry. The activity is best suited for grades 3-5, but could be modified for higher levels. The investigation can be done with an entire class, and includes a short field experience combined with a classroom activity. The field experience portion needs to be done in the fall, when there are still leaves on the trees or in May/June. At least four lesson times would be needed for this activity. The necessary equipment is a field guide for trees, a short story involving trees, and possibly chart paper for the group presentation. A digital camera is optional.

Online Tree Care Advisors Resources:

A Walk in the Forest- Virtual Tree I.D.

Minnesota Tree Type Guide

Tree I.D. Book- will work if you don't have access to the online material.

Description and Teaching Materials

Depending on the grade level the activities listed can be modified so that all students of all ages can benefit. Activities can be done together as a class; or depending on the maturity level of the students they can be divided into small cooperative learning groups.


The Giving Tree, By Shel Silverstein
Tree I.D. Guide
Digital camera (optional)
Science notebooks/journals (optional)
Chart paper (optional)

Warm-Up - Read to students a book about trees. A common example is The Giving Tree by Shel Silverstein. If the students are not familiar with OKWHL introduce these terms at this point. (O - What I observe K - What I know, W - What I want to learn, H - How, and L - What I've learned). Tell students they are going to spend some time learning to identify trees in their neighborhood.

Activity 1 - Start a OKWHL chart to be used for the entire lesson. List all the things students know about trees. (This is the K step of OKWHL.) Lead students in a discussion of how to identify trees. Guide students to list all the things they may need to know to identify trees in their neighborhood. (This is the W step of KWL.)

Activity 2 - Students may have listed leaves as a means of tree identification in activity 1. Continue discussing leaves as a means of tree identification. Introduce leaf terminology at this point. (See information page) shape, margins, venation, petiole, etc.

Activity 3 - Students will go on a field trip around the school to collect leaves from as many trees as possible. (If there are no trees on school grounds, a field trip to a nearby park may be necessary.) Remind students to be careful not to damage trees and surrounding grounds. Students may also use a digital camera to photograph the trees for future reference and later activities. A homework extension could involve students gathering leaves from their own yards.

Have students gather 3 or 4 leaves from different trees. If possible collect bark (do not pull leaves or bark from trees, collect from the ground). They may also do an optional bark rubbing in their science notebooks.

Explore some of the things that make leaves unique. Close observation of trees in the school grounds. Students to be encouraged to observe closely the trees to see:
  • What color the leaves are.
  • How big or small the trees are.
  • If the tree has many or a few leaves.
  • If the leaves grow far apart or close together.
  • What color the bark is.
  • How the bark feels.
  • What the flowers, berries, nuts look like.
  • What the root system looks like. Can it be seen?
  • How old the tree might be. How could we find out?

Investigate different kinds of trees and how they grow. Identify trees by their bark and leaves. Take photographs of trees/leaves/bark, label. In science notebooks/journals, students can be encouraged to draw a picture of various trees and/or write a description.

Leaf Sorting:

Students to sort, list, and label their collected leaves (students to work in groups of three). Students should come up with these categories on their own if possible!
  • By size - large to small, wide to narrow, long to short.
  • Texture - rough to smooth, thick to thin.
  • Insect damage - leaves with the most holes to those with the least, leaves with the most bumps or other kinds of damage.
  • Colors - reds, yellows and other shades of foliage, or variations of green.
  • Smell - leaves with a pleasant smell, with an unpleasant smell, with no smell.
  • Edges - leaves with smooth edges, leaves with 'teeth'.

With another group, students discuss the different categories they created.

Display students' charts.
Students compare and study leaves.
  • Describe how leaf shapes, sizes, differ from tree to tree.
  • Look for differences in your leaves?
  • How are your leaves the same?
  • Do you see any hairs?
  • Do they feel rough or smooth?

Each student will select one of their leaves and find other students with the same leaf. Form groups. Each group writes adjectives to describe their leaf. Share with rest of the class. Teacher modeling - make a Venn diagram

Activity 4 - Students select one tree type to research. Working together in small groups, students list the questions about the tree they would like answered. Using resources from the learning center, students read to find the answers to their questions. The teacher will need to provide support to some students to help them find answers to their questions.

Extension Options: Math and Social Studies

Teachers may also make it an option for students to measure the length of their leaves and make a graph to compare the different length leaves of various types of trees.

Teachers may also have some student groups research trees that are not found in Minnesota, or even North America. Teachers could have students discuss the geographic locations of these trees as well as some of the differences that these trees have from the trees found in Minnesota.

Teaching Notes and Tips

A practical tip for this lesson is to limit how far students go for the field work. Also, it would be helpful for this activity to be done after classroom procedures and climate have been well established. For example, material collection and group dynamics. It is important to know the strengths and weaknesses of your group to anticipate where you might have to step in with some guidance. In addition, if you have students gather leaves from home, it helps to have them bring in the leaves on the stem to further help identify the tree of origin.


Informal assessment of student understanding will be made using targeted questions of the class. Student presentations could be either informally or formally assessed. Additional formal assessment of the concepts will follow the close of the unit of study.


4th Grade
I.B.2, Scientific Inquiry
IV.B.1 & 2, Diversity of Organisms
I.B.1, Vocabulary Expansion

References and Resources

The Giving Tree, By Shel Silverstein

Dichotomous Tree Identification Guide- See website above

A Walk in the Forest- Virtual Tree I.D.

Minnesota Tree Type Guide