Tree Identification

Previous: Botany of Stems, Roots, & Flowers

Tree: Woody structure that grows every year, typically with one trunk, and lateral branches.

Questions to ask when trying to identify a tree:

• Do the leaves have needle-like shapes? Or are the leaves a broad shape?
• If you have a broad leaf, you then want to distinguish whether you have a simple leaf or a compound leaf....

Simple leaf - one blade per one petiole

• the petiole is the stalk that joins the leaf to the stem/branch
• If you follow the petiole to the branch, you will find a leaf bud (next year's growth).

Compound leaves - multiple leaflets attach to a rachis, petiole, or leaf stalk

• How do you know this is a compound leaf and not just a collection of simple leaves?
  • You can follow the petiole back to the branch and you will see a little bud at the base of the petiole.

Branch Arrangement

Most trees have an alternate arrangement - branches, leaves, and buds come out singly in an alternating pattern.

A smaller percentage of trees have an opposite arrangement -  buds, leaves, and branches come out in opposite pairs.

Whorled arrangement - leaves, buds, and branches are arranged in evenly spaced groups of three. (Northern Catalpa is the only tree in Illinois that has a whorled arrangement).

Whorled arrangements are more common on herbaceous plants (cleavers) and shrubs.

Remember the phrase: "The MAD Bucking Horse Whorled the Cat":

I know, it’s a little intense, but it might help!

• M = Maple
• A = Ash
• D = Dogwood
• Bucking = Buckeye
• Horse = Horse Chestnut
• Whorled the Cat = Catalpa

The trees above are the most common trees in our area that do not have alternately arranged branches, leaves, and buds. Maple, Ash, Dogwood, Buckeye, and Horse Chestnut all have oppositely arranged branches, leaves, and buds. ‘Whorled the Cat’ indicates the one tree species in our region that has a whorled arrangement of branches, leaves, and buds. Some smaller shrubby, woody, plants (honeysuckle, viburnum) have opposite arrangement. All other large, single trunked, broadleaf trees will have an alternate arrangement.

Distinguishing Common Conifers

• Pine needles are clustered in bundles (called fascicles).  Depending on the species of pine, there may be two, three or five needles per bundle. Pine cones tend to stick out in various directions.
• Both Spruce and Fir needles attach directly to the twig, not in bundles.
• Spruce needles are sharply pointed, square, and easy to roll between your fingers. The needles are attached singly on the twig, but on small woody pegs.  The cones hang down.
• Fir needles have a softer, flatter feel than Spruce, cannot be rolled be rolled between your fingers and are attached singly and directly to the twig.  Fir cones stand upright.

Also consider when identifying:

• Flowers
• Fruit
• Bark
• Form (shape or silhouette) – it's great to look closely at a tree, getting a sense of the characteristics of buds, twigs, etc. But a lot can be deduced by taking a step back and looking at the tree's size, color, and form. Every species of tree has a typical form (shape or silhouette) that it will attain as it matures.
  • For example, Linden trees tend to take on a characteristic 'Spade' like shape in maturity (as in the 'Ace of Spades').
• Habitat - sycamores and willows grow in moist/wet conditions so you might find them growing by rivers or ponds.
  • If you don't know what a plant is, make note of the habitat. When IDing, does the habitat match with the ID you made?
    • If you are in a swampy area and have determined a plant is a kind of Milkweed (Asclepias spp.), you can probably assume it's not Butterfly Milkweed (Asclepius tuberosa) which grows in drier areas. You can likely deduce that the plant is Swamp Milkweed (Asclepias incarnata).
• Season – trees change significantly from season to season, the only way to really know trees is to observe them throughout all seasons.