It is not at all easy to recognize oak leaves. In the United States alone there are over sixty species and in the rest of the world there are hundreds of different varieties. To try to narrow it down as much as possible, you can divide oaks into two basic categories by looking at just the shape of the leaf: red oaks and white oaks. Learning the differences between these two types is the first step in identifying a leaf of this tree.
Steps
Part 1 of 2: Studying Leaves Effectively
Step 1. Distinguish oak trees from other trees
They are part of the Quercus genus and are widespread in all regions with a temperate climate. There are more than 600 known species, of which 55 are found in the continental United States. Since the variety is so wide, there are very few characteristics that they have in common.
- Acorns: this is the main feature that makes you understand that you are facing an oak. If the tree produces acorns, it is an oak.
- Lobate leaves: these are leaves whose margin has rounded or pointed indentations that extend from the median line. Although there are few oaks with non-lobed leaves, they are generally all rounded symmetrically to the center line.
- Thin and scaly bark: Oak bark is a variable detail, but is typically made up of small hard scales. It is very different from that of pines (made up of large crumbly pieces) or that of birch (which looks like wallpaper), it has many more cracks and incisions.
Step 2. Look at the tips of the leaf lobes to determine if it is a white or red oak
The lobes are protrusions along the leaf margin that extend on either side of the center line, as if they were the tips of a star. This is an important distinction, because it allows you to exclude half of the possible trees.
When it comes to red oak, the secondary ribs extend all the way to the edge, creating the lobes
Step 3. Consider the area you are in
Each area of the world has its own specific "assortment" of oaks, which is often very different from that found in other regions. The species you can encounter change depending on where you are; for example, it is rare to find an oak tree on the west coast of the United States that is generally present in the east, just as it is practically impossible to find a tree native to the northern regions in the south. You can then use this criterion to your advantage to understand the type of tree in front of you. Here are some examples that apply to the continental United States.
- Generic division of regions: north-eastern; south-eastern; north-western; southwestern.
- Coastal or inland regions.
- Mountainous or lowland areas.
Step 4. Count the lobes on each leaf
The lobes are the protuberances present on the margin of the leaf and which extend from the center to both sides. If possible, compare different leaves to find the average number of lobes. Some species, such as quercus phellos, have smooth-edged leaves, but most trees in this genus have lobed leaves.
Consider at least 4-5 leaves to identify the oak, as this will be an important detail when you consult your nature guide
Step 5. Measure the leaf incisions
Observe the space between one lobe and the other to understand the depth of the incisions. The leaves of the white oaks have notches of variable depth that alternate in a random way; the leaves of the red oaks, on the other hand, have very deep, pointed or paradoxically no notches.
Step 6. Observe the color changes in the fall
The leaves of the evergreen oaks are bright and dark green throughout the year; however, most of these trees change color in the fall; some oaks, such as quercus coccinea, show off bright colors this season, while white oaks and quercus prinus turn a dull brown.
In summer, observe if the leaves are dark or light green, if they are shiny or not; all these details allow you to recognize the varieties
Step 7. Measure the size of the leaves
Evergreen oaks and some varieties of red oaks (quercus pacifica, quercus coccifera, quercus geminata, and others) have smaller leaves, while most red and practically all deciduous oaks have very large leaves (at least 10 cm). This is one of the most important characteristics for distinguishing similar species of this tree.
Step 8. You can identify unknown species with a herbarium or nature guide in your area
Thanks to the information you have gathered, you can recognize the plant using these books. There are hundreds of oak trees in the world, so don't expect to know them perfectly. Use the criteria described so far to narrow the search field and then consult the guide to understand which oak you are looking at. You can read the list below or consult the website of the forest ranger or an association for the defense of the environment.
- Go to the correct section of the guide. Most of these herbaria are divided into sections for red and white oaks.
- Narrow the possibilities to the species native to your area. A good guide should also have a distribution map of each species.
- When you have made a list of possible oaks, compare the images with the tree in front of you, to understand which one it is.
Part 2 of 2: Recognizing Some Common Oaks
Common White Oaks
Step 1. Identify a quercus alba by looking at the lumpy, scaly acorns
This tree is characterized by scaly acorns, with the surface covered with wart-like bumps and a light-colored bark. Its leaves have:
- Five to seven lobes that fan outwards as they approach the tip;
- Incisions that end approximately halfway between the edge and the central grain;
- Bright light green color.
Step 2. Recognize the quercus stellata
This is typical of the central-western regions of the United States, has a dark bark and characteristic leaves:
- There are generally 5 lobes;
- The lobes are arranged in a cross;
- The texture is similar to leather, the surface is thick and dark in color.
Step 3. Identify a quercus macrocarpa
This tree is found throughout the US Midwest, has huge leaves and typical acorns that have a dome (a kind of "hat" located at one end) of considerable size that hides almost all the fruit.
- The leaves can grow up to 30 cm in length;
- The margin has broad and almost always flat lobes.
Step 4. Identify a quercus prinus
It often grows in rocky soils and is a widespread tree that produces reddish-brown or dark brown acorns and has a very wrinkled bark.
- The margins of its leaves resemble the edge of a serrated blade and the secondary veins do not reach the tips;
- The leaf is very broad at the tip and narrows towards the base;
- The length of the leaves is between 10 and 22.5 cm, while the width is around 10 cm.
Common Red Oaks
Step 1. Recognize quercus rubra
This fairly common oak produces flat-tipped acorns, reminiscent of the pork-pie hat (flattened dome and folded up brim).
- The leaves are light green and have 6-7 lobes;
- The incisions stop about halfway from the central grain;
- The pointed lobes may have two small spikes on the other side.
Step 2. Recognize a quercus shumardii
The dome of its egg-shaped acorns covers only ¼ of the fruit, the bark of the plant is straight and light in color. It is a tall tree that can reach 30 meters.
- The leaves have a dark green color;
- The lobes are divided at the ends into small teeth similar to pointed bristles;
- The incisions are very deep.
Step 3. Quercus palustris
This oak is a very common decorative tree that grows quickly and produces characteristic acorns that have a dome-like dome. The bark is smooth and gray.
- The thin leaves have deep incisions that make them appear very tapered;
- They have 5-7 lobes that divide into different points at the extremity;
- The leaves have very intense colors even in autumn;
- The quercus ellipsoidalis variety has very similar leaves, but produces much longer acorns.
Step 4. Quercus velutina
This has no distinctive leaves, but the inner part of the bark is orange and you can often see it through the cracks on the trunk.
- The leaves have a dark green color;
- The leaves are large, up to 30 cm long and wider in shape at the tip than at the tip.
