Tuesday, June 11, 2013

Leaf Identification - If 3rd Graders can do it, why can't you?

One of the classroom activities that I do with 3rd Grade students is a program on Michigan Trees.  There are two hands-on parts to this program.  The first involves tree "cookies" or cross-sections of trunks.  Many of the students know that you can count the growth rings on a tree to determine the age of a tree, but most have never done it before.  In addition to counting the rings, I also have the students measure the diameter of the tree, figure out when the tree started growing, and draw the growth rings - remember this is with 3rd Graders.

The second hands-on part of this program is a leaf classification activity.  Several years ago, I collected a number of real leaves that can be found locally in Mid-Michigan (most of the trees are native species).  I pressed and dried these leaves.  Then placed these leaves on a sheet of cardstock and ran them through a laminating machine.  Add a sticker for a label, and you have a set of leaves that can be used for years.  I also made photocopies of all the laminated leaves and scanned many of them into the computer. 

 For the leaf classification activity, each student/group of students is given a packet of leaves (laminated/color copies/black & white copies).  First the students are asked to determine if the leaves belong to a needle-leaf tree or a broadleaf tree.  Most of them get this fairly quickly - once in a while a student gets tripped up by the fact that many broadleaf trees have leaves with "needle-like" teeth or points.  Basically, if the leaf is VERY narrow and shaped like a needle, it is a needle-leaf tree.  The next four leaves are all examples of needle-leafs.


The next leaf is also classified as a needle-leaf, even though the leaves do not look like a needle.  Instead the leaves are shaped more like fish scales, but for the purposes of this activity, it gets classified as a needle-leaf.

So what makes a leaf a broadleaf?  It is wider or broader than a needle-leaf.  Basically any leaf that is not a needle-leaf is a broadleaf.  Here are three examples.

As you can see, there is a lot of variation in the shape and size of broadleafs.  Identifying a needle-leaf is much more straightforward - if its leaf looks like a needle, it's a needle-leaf.  The classification of broadleafs can be further expanded to include simple leaves and compound leaves. (I know needle-leafs can be simple of compound also, but when working with 3rd Grade students it's best not to make the classification overcomplicated).

A basic definition of a a simple leaf is that if it has one leaf on one stem its simple.  This Quaking Aspen leaf is a good example.  It has a very basic shape with a margin (edge) that has only small teeth.  It is easy to see that this is a simple leaf.

However, the margins of all broadleafs are not this simple.  Many broadleafs have leaves that are divided into lobes.  This can be confusing to younger students, but if the margin of all parts of the leaf are connected (meaning it does not go all the way back to a stem and form a new leaf) it is still a simple leaf.

 Maple leave are good examples of broadleafs with lobes.

Oaks also have lobes.  The lobes on many oaks are deeply divided, but the margin is continuous all the way around the leaf - so again these are simple leaves.

On a broadleaf with compound leaves, the margin of the leaf is not continuous.  The leaf is divided up into multiple smaller segment called leaflets.  Basically if it looks like there is more than one leaf on each non-woody stem, the leaf is compound.  These leaves may have as few as three leaflets like this one.

It may have five leaflets.

It may have seven leaflets.

Or it may have more leaflets.  Sometimes the leaflets are further divided.  Sometimes the leaflets are lobed.

Leaf classification does not have to be complicated.  If you remember a few simple things you can easily place leaves in a few categories like needle-leaf and broadleaf, and simple and compound leaves.

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