During autumn, the leaves change colour and texture because the days are colder and shorter. This causes the trees to get less sunlight, which causes the pigment in the leaves, chlorophyll, to break down. Chlorophyll gives leaves their green colour, and due to a lack thereof, the leaves appear orange, red and yellow. The leaves dry out due to the cold and lack of sunlight as well. These conditions cause a decrease in a auxin, the hormone that helps trees grow. This decrease weakens the connection between the tree and the leaves. After a while, this connection grows weak enough that the leaf is no longer receiving and nutrients, and breaks off and dies.
During the activity, learners collect both green and discoloured (yellow and orange) leaves. They observe and compare the texture and colours of these leaves with magnifying glasses and paste them down on paper to create a tree.