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Leafy Learning: Identification Characteristics for LeavesKnowing how to describe a leaf can help you identify trees.
Leaf Arrangement
Simple leaves look like one leaf with one blade and one petiole. They can be different shapes but always have only one blade.
Simple CompoundCompound leaves look like they are made up of many leaves, but they are only one leaf. The leaf blade is divided into leaflets. These leaflets look like small leaves. Some leaflets are divided again and so they are made up of subleaflets. These leaves can be different shapes.
Leaf vs LeafletSo how can you tell a leaf from a leaflet? Leaves join onto the tree’s twigs whereas leaflets join onto the leaf ’s midrib. Where a leaf is pulled off a twig, it leaves a leaf scar and you may see a bud. Where a leaflet is pulled off a leaf ’s midrib, there is no bud or large leaf scar.BladeMidrib
Midrib
Petiole
Blade
Leaflet
Subleaflet
Petiole PetioleLeaflet
Leaf
Leaflet
No LeafScar
Twig
Leaf Scar
Bud
Midrib
Midrib
One Leaf One LeafSeven Leaflets
One LeafSix Leaflets
Thirty Subleaflets
a a a
page 1
Leafy Learning: Identification Characteristics for Leaves
Being able to describe the margins of a leaf is important.
Twig Arrangement
Leaf Margins
Margin (edges of the leaf blade) is smooth.
EntireMargin has teeth. The teeth can be fine and small, coarse and large or even doubled.
ToothedMargin is indented and wavy. Lobes can be sharp or rounded.
Lobed
The orientation of the veins, lobes and leaflets. Leaf Venation
Veins, lobes and/or leaflets radiate from one point, like your fingers from your palm.
PalmateVeins, lobes and/or leaflets start in pairs from the midrib of the leaf blade.
Pinnate
How leaves grow along a twig or branch can be very helpful in identification of trees. Most of our trees have leaves that grow in an alternate arrangement from the twig. A few of our trees, such as maples, ashes and dogwoods, grow in an opposite arrangement (local botanists use the first letter of these trees’ names and call this the MAD principle). A rarer type of arrangement is called
whorled. This type has the leaves growing off the twig in bunches of three or more.
Alternate WhorledOpposite
Twigpage 2
Leafy Learning: Identification Characteristics for LeavesThis sheet shows many different types of leaves. Can you understand how each of these leaves got its name?(note: “bi” means “two”)Simple Entire Simple Toothed
Simple PinnatelySharply Lobed
Palmately Compound Pinnately Compound Bipinnately Compound
Simple PinnatelyRounded Lobed
Simple PalmatelyLobed
page 3
Leafy Learning: Identification Characteristics for Leaves
Activity #1 - Test Your Knowledge
Now that you’re a leaf expert, let’s test your skill! Using the “Native Tree Leaves in your Neighbourhood” biodiversity, sort the following leaves into the appropriate columns. Go back to the leaf characteristic sheets if you need help!
Red Maple, Honey Locust, Ohio Buckeye, Staghorn Sumace, Tulip Tree, Kentucky Coffeetree, American Beech
Leaf Arrangement
Simple Bipinnately CompoundPinnately CompoundPalmately Compound
Now, let’s take a look at leaf margins. Using the “Native Tree Leaves in your Neighbourhood” biodiversity sheet, sort the following leaves into the appropriate columns:
Tulip Tree, Sassafras, Elm, Common Hop-Tree, Paw Paw, Black Walnut, Birch
Leaf Margins
Entire CompoundToothedLobed
page 4
Leafy Learning: Identification Characteristics for Leaves
Activity #1 - Test Your Knowledge continued
Now you’re ready for the big test! Can you correctly classify all of these leaves from your “Native Trees in your Neighbourhood” sheet? Kentucky Coffeetree Black Walnut Mountain-Ash Ash Ohio Buckeye Sugar MapleAmerican Sycamore Tulip Tree Red Oak Bur Oak Redbud Largetooth AspenHackberry Ironwood American Beech Hawthorn Dogwood Paw Paw
All Leaf Characteristics
Simple Entire Simple Palmately Rounded Lobed
Simple PalmatelySharply Lobed
Simple Toothed
Simple Palmately Lobed Bipinnately CompoundPinnately CompoundPalmately Compound
page 5
Leafy Learning: Identification Characteristics for Leaves
Activity #2 - Outdoor ResearchOutside Time! Now that you are a trained botanist (someone who studies plants), you can out into your yard and/or neigh-bourhood and look for tree leaves. In general, a tree is a plant with a single, woody, permanent trunk growing out of the ground (there are exceptions, of course). Put a checkmark in the appropriate Leaf Type box for each leaf you find. Also, put a check-mark in one of the three Twig Arrangement boxes. When you are done, look at your data. What do you notice? What is the most common leaf type or the most common twig arrangement? Scientists don’t have perfect answers on why different tree species have differently shaped leaves or twig arrangements. Maybe you can solve the puzzle someday!
Simple Entire Simple Palmately Rounded Lobed
Simple PalmatelySharply Lobed
Simple Toothed
Simple Palmately Lobed Bipinnately CompoundPinnately CompoundPalmately Compound
Alternate WhorledOpposite
Twig Arrangement
Leaf Type
page 6
Leafy Learning: Identification Characteristics for Leaves
Don’t forget the Conifers!Did you know that pine needles are actually leaves? They are just very tough leaves that can live through the winter (though there are exceptions). There are twelve native conifer trees in Ontario. While telling some of the individual species apart can be tricky, knowing the basic groups of conifers is not too difficult.
Pines Red-CedarWhite-CedarTamarack
- needles short and four-sided (they roll in your fingers well)- needles project from all around the twig, making it look like a brush
- needles are two-sided and flat- needles project mostly on sides of the twig, making it look like a feather- needle joins the twig with a ball-shaped swelling
- needles are two-sided and flat- needles project mostly on sides of the twig, making it look like a feather- needle joins the twig with a little stem-like projection
HemlockFirSprucesPines
- long and slender needles in bunches of two, three or five- always check more than one bunch of needles on a tree because sometimes individual needles may be missing from a bunch
- needles in bunches of more than 5- needles very soft and short- needles turn yellow and fall off every autumn
- needles are flattened into small scales- branches of needles soft
- needles are either very sharp and pointed or tiny soft scales - branches of needles often prickly
Red-CedarWhite-CedarTamarack
Activity #3 - Evergreen Eyes Go outside and find some evergreens (another word for conifers). Put a check in each box for each one your find. Which species group is the most common in your area?
Spruces Fir Hemlock
page 7