A Little Bit More
Maybe it seems like a small point to focus on “simple” leaves as opposed to “compound” leaves, after all that’s more for botanists anyway, right? Actually, knowing the difference is very important even for the casual person who wants to identify a tree in their backyard. Knowing the difference between simple and compound leaves is a vital step in the identification process.
Elm leaves on branch and an individual leaf
I first realized the importance of distinguishing between compound and simple leaves when I was asked to help a group of 7th graders identify and arrange their leaf collections. Although the teacher had discussed the difference between simple and compound leaves before they began, it was soon obvious that most had not understood or not integrated this information before they began collecting. Many of the students brought in only one “leaf” from each of their selected trees and I was presented with a mix of leaves AND leaflets with no other identifying information – what a confusing mess! Actually, this may have been helpful as we used this opportunity to review the criteria for collecting “entire” leaves and the students now understood what was needed.
Ash leaves on branch and an individual leaf with leaflets
It can be difficult, at times, to distinguish between leaves and leaflets. As the unit poster notes, the real test is whether or not there is a bud nestled at the junction of the leaf stalk (petiole) and twig. The bud represents next year’s growth and always forms at the base of the true leaf.
Activities
Science – Leaf or Leaflet?
Objectives: Get a good look at some leaves in situ
Materials: Local trees
I think the best way to further the value of this unit would be to visit some local trees and take a close look at their leaves. Once the buds open on your trees, you should have many months in which you can examine leaves. Be sure to look closely at each complete leaf, or what you think is a complete leaf, and look for the bud at its base. Once you’ve done this a few times on various species of trees, your students should have a much better idea of the differences between leaves and leaflets.
Some species that have compound leaves with leaflets include:
Black Walnut
Ashes
Box Elder (really a maple)
Locusts
You can also check out leaves in a tree field guide before you go outside to see which trees are most likely to be found growing in your area, though it is always possible for introduced trees to confuse the issue.
Nature doesn’t always play by the “rules” so in some species, the leaflets may be lost before the main stalk falls in autumn. It’s not uncommon to see locust “skeleton leaves”, the leaf stalk or rachis, clinging to a tree after the tiny leaflets have fallen off so don’t let this throw you off.
Science – Leaf or Leaflet?
Objectives: Get a good look at some leaves in situ
Materials: Local trees
I think the best way to further the value of this unit would be to visit some local trees and take a close look at their leaves. Once the buds open on your trees, you should have many months in which you can examine leaves. Be sure to look closely at each complete leaf, or what you think is a complete leaf, and look for the bud at its base. Once you’ve done this a few times on various species of trees, your students should have a much better idea of the differences between leaves and leaflets.
Some species that have compound leaves with leaflets include:
Black Walnut
Ashes
Box Elder (really a maple)
Locusts
You can also check out leaves in a tree field guide before you go outside to see which trees are most likely to be found growing in your area (always possible for introduced trees to confuse the issue).
Nature doesn’t always play by the “rules” so in some species, the leaflets may be lost before the main stalk falls in autumn. It’s not uncommon to see locust “skeleton leaves”, the leaf stalk or rachis, clinging to a tree after the tiny leaflets have fallen off so don’t let this throw you off.
Key Concepts
Structures and Functions, Identification
Questions
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