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Tips to Identifying a Tree By its Leaves

As residents of the Pacific Northwest, we enjoy being surrounded by trees. We plant them in our backyards. We adore them as we careen down Cornell Boulevard. We especially take a gander when roaming our local green spaces, like Laurelhurst and Forest parks. But, do you know what you’re looking at?

Do you ever wonder what trees you were so fondly ogling and wish you had the knowledge to know more about the natural environment you so greatly appreciate? This happens so often that we’ve decided to let you in on how to identify a tree by looking at its leaves.

How to Identify a Tree By its Leaves

While leaves are just one component of a tree, often that’s all you need to know, and this is a particularly important skill as poisonous trees can often be spotted using this method. But let’s start simple.

Conifers

Does the tree you’re looking at have leaves that you would actually identify as needle-like? You’ve just spotted a conifer, or cone-bearing, tree, and these are often evergreen.

Are those needles in clusters of 2-5? Then you’re looking at a pine tree.

Are those needles in clusters of 2-4 with a prickly cone, or mostly in groups of 5 with smoother cones? The first would be a pinyon pine. If the later also has slender needles that are 2-4 inches long, with thin, smooth cone scales, and cones 12-26 inches long, then you likely found a sugar pine. Is the cone 8-11 inches long instead? Then, it’s a western white pine.

Let’s start over. What if you find a tree that has needles arranged on short, spur-like branches and is deciduous (not green all year)? Then you just came upon a western larch.

Evergreens

As you continue your path through the park, you come upon another grouping of trees. This time it has scale-like leaves and cones that sometimes resemble berries. If the cone is also oblong, ¾-1.15 inches long with 6, thin leathery scales and hangs down, then you likely just came upon an incense-cedar. If, however, the cones are smaller, have 6-12 scales, and stand up, then it’s likely a western red cedar.

What if it’s not either of those? Then if the fruit is berry-like and has a whitish, waxy covering, it’s probably a juniper tree. If the bark of the juniper is arranged in thick, square plates, it’s an alligator juniper, but if it’s fibrous and shreddy instead, and the tree has reddish-brown bark it’s either an eastern red cedar or rocky mountain juniper (more blue-green). However, if the bark is grey then you’ve come upon a non-native juniper; either one-seed or Utah.

Broadleaf Deciduous

These trees have flat, thin leaves, and come and go with the seasons, so you’ll only see these leaves during the right time of year. However, when it happens, this is what you’ll be looking at.

If the leaf you’re looking at is a simple one blade leaf that attaches directly opposite one another on the same twig, if the leaves are lobed and have sharper edges with more defined dips (sinus), and it’s medium to large in height, you’ve narrowed it down to two varies. If the leaves are 6 inches across with 5 lobes, it’s a silver maple. If the leaves are 4 inches across with 3-5 lobes, it’s a red maple.

Let’s start over. What if you come across a tree that has simple leaves that alternate growth along a twig? If the leaves are fan-shaped, it’s ginkgo biloba. If not, but the leaves are irregularly lobed and longer than 1 inch on a twig with thorns, and contains black, berry-like fruit, you’ve come upon a black hawthorn.

Poisonous

Have you ever completed a hike only to notice later that you have a rash? It was likely caused by urushiol, an oil found on poison ivy, oak, and sumac that is poisonous to most humans, triggering an immune reaction. This rash will likely appear between 1-3 days after your exposure and is known to last for weeks. If you’ve been in contact with one of these three plants, have a very itchy, red rash, often appearing as bumps or streaks, then this is likely the reaction you’re seeing.

But, how can we avoid these plants in the future? This is what you can look for on your next hike.

Poison oak grows wild as a shrub and is about 3 feet tall, but can also climb up oak trees; that’s how it got its name. This plant is also native to our region, so if you haven’t seen it yet, you probably just haven’t been looking for it.

It usually has leaves that come in groups of threes and alternate up the stem. It may also contain small flowers or white berries. The worst part about poison oak leaves is that they vary dramatically. Some are toothed, others lobed; some are glossy, and others are dull; they also range between 1-4 inches in length. For this reason, it’s tricky to notice, but keep the cluster of three leaves in mind and stay away from anything similar.

Like poison oak, poison ivy also has leaves that grow in groups of threes. The leaves are often pointed at the tip, and represent as a dark, waxy green in the spring and red-orange in the fall. It is found as both a vine and a shrub.

Poison sumac is generally easier to ID. A sumac tree is between 6-12 feet tall, has smooth-edged leaflets with 5-13 leaflets per stem, the new bark is smooth and older bark is rough, and it has green, odd-shaped berries in summer and white berries with colorful leaves in the fall.

It’s Not Easy

As you can interpret, identifying a tree from just it’s leaves, while entirely possible, is not easy. But today, you don’t have to learn how to identify a tree from its leaves. Instead, you can just download the free app called Leafsnap.

This ingenious technology, a collaboration between Columbia University, the University of Maryland, and the Smithsonian Institution, uses the same mathematical techniques used to develop facial recognition and applies it to nature.

If you’re not an amateur arborist, identifying trees as you stroll along is not a simple task, but if you see one you want to plant in your yard or have questions on if a tree is viable in your space, reach out to Mr. Tree with questions. We’re always glad to assist.