Objectives
Students will be able to identify some common trees by their winter twigs.
Method
Students will study and collect winter twigs from trees growing in their area.
Materials
clippers or knife; tree identification guide; and plastic spray
Background
Usually, we recognize deciduous trees and shrubs by the shapes of their leaves. However, winter is an excellent time to identify different plants by their twigs. It may seem as though bare, leafless trees have stopped growing in winter, but plants are always up to something interesting. Depending on the season, they are continually channelling energy and food to some parts, and withholding them from others. For instance, each summer, trees actually grow their leaves for the following summer! You can find them folded neatly into the scale-covered buds along twigs and limbs. Late in summer, trees “know” how to keep these buds from unfolding, while at the same time, they are growing this year’s seeds and fruits.
In winter, trees also know how to control their growth to save energy during the cold months. This phenomenon is one reason why they shed their leaves. They also know just when it’s time for their buds to start unfolding into leaves and flowers in the spring. Unseasonable warm spells during winter thaws don’t fool them into growing their leaves too soon! Clues like longer days and chemical changes inside their cells let the trees know that spring is really here and it’s safe to get growing!
The six most common deciduous trees are oak, maple, ash, beech, birch, and trembling or quaking aspen. Students who learn to identify these species, along with the evergreens, will be able to identify at least 80 per cent of the trees growing in most northern forests.
Procedure
- Go outside with the class and collect twigs from different kinds of trees.
- Back in the classroom, classify the twigs using an identification guide. A partial identification key is provided in this activity.
Extensions
- (Younger students) Give each student a twig and have them find another student with a twig that matches their own.
- Go on another hunt, but this time look for different-coloured twigs, such as yellow willow or red osier dogwood.
Evaluation
Mount the different types of “tree” on a large piece of posterboard. Spray twigs with several coats of plastic spray and let them dry. Label the results and post in your classroom.
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