There are literally hundreds of oak species scattered around the world. This popular tree provides shade, has beautified the landscape for centuries, and continues to be very common in gardening projects. To accurately identify oak trees it is important to study some peculiar characteristics that make them unique and beautiful.
Steps
Method 1 of 4: Recognizing the Varieties
Step 1. Pay attention to the size of the oak family
There are about 600 distinct species that are part of the Quercus genus; in most cases these are trees, although there are some shrubs. Some varieties are evergreen, while others are semi-evergreen.
- These trees are native mainly to the wooded regions of the Northern Hemisphere, but their diffusion is very wide: from the cold and temperate forests of North America and Europe, to the tropical jungles of Asia and Central America.
- It is rather difficult to be able to make a taxonomic subdivision of oaks, due to the great variety of trees and high hybridization. In the United States, for example, it is common to indicate with the name "live oak" a series of evergreen trees and shrubs that are not necessarily related to the genus Quercus; these can still be considered oaks insofar as they belong to the evergreen variety.
Step 2. Find out about the species growing in your region
Get an illustrated botanical guide of the area you live in and take it with you on walks in the woods; the pictures are of great help in your attempt to recognize specific oak varieties.
- In North America, trees are divided into two large groups: the "red oaks" and the "white oaks". The former have a darker bark with lobed and pointed leaves; the latter have a lighter bark and leaves with rounded lobes.
- Among the "white oaks" are mentioned: Quercus muehlenbergi (lives in soils rich in limestone), Quercus virginiana, Quercus marilandica (found on dry ridges), Quercus imbricaria (lives along steep and humid soils), Quercus michauxii (present in marshes), Quercus alba (widespread in various ecosystems), Quercus bicolor (in swamps) and Quercus lyrata (lives in marshy soils and in stream beds).
- The most common "red oaks" are: Quercus nigra (lives near stream beds and in lowland areas), Quercus rubra (widespread in various habitats), Quercus falcata (thrives on steep wet and dry soils), Quercus phellos (it grows on steep humid soils), Quercus palustris (in swamps) and Quercus pagoda (can be found on wet ridges and valleys).
Method 2 of 4: Recognizing Oak Leaves
Step 1. Learn to recognize leaves
Observe the lobed edges that follow a sinusoidal pattern with more or less rounded indentations and protuberances.
- The lobes are the rounded or pointed parts that give the leaf its characteristic shape. Consider these elements as the "fingers" of the leaf or the extensions of the stem; the various species of oak can have pointed or rounded lobes. Trees belonging to the red oak group have leaves with a serrated edge, while white oaks produce leaves with a rounder lobed outline.
- Between one lobe and the other there is a recess that accentuates the shape of the protuberance; the indentations can be deep, superficial, wide or narrow.
Step 2. Look closely at the leaf
The shape also varies between leaves on the same tree, and you need to examine several of them before coming to an accurate classification.
- If you are unable to trace the name of the species through the characteristics of the foliage, consider other characteristics, such as the acorns, the bark and the place where the tree is located, both in terms of soil type and geographical location.
- The leaves develop following a spiral pattern around the branch; consequently, it is rare for a group of them to appear "flat" or aligned, just like the foliage of palm trees.
- Oak branches tend to split in a straight line without opposing each other - imagine a fork with several tips that all have the same origin.
Step 3. Look for green leaves in summer, red in autumn and brown in winter
Most oaks "sport" a beautiful deep green foliage during the summer months, which then turns red and brown in the fall.
- Oaks represent the most colorful trees of autumn and this is another reason why they are used so much for garden design. Some varieties produce foliage with red or pink hues in early spring, then change to standard green during the summer.
- These trees tend to lose their leaves quite late; specimens or young branches are able to retain brown leaves until spring, but drop them when new shoots appear.
- One clue that allows you to recognize an oak is the presence of dead, brown leaves during the winter. These trees have a slower rate of loss of leaves, which remain close to the oak longer; you can usually find them at the base of the trunk, but be wary, as they can be blown away on a windy day.
Step 4. Use the features of the foliage to distinguish white from red oaks
- The species belonging to the white oak group may have reddish-brown leaves when autumn approaches, while those of the red oaks give a more pronounced effect: they reach an intense and deep red shade that stands out clearly in the woods during late autumn.
- Red oaks are often confused with maples. Maple shows autumn colors early in the season and runs out of almost all pigments before the oak foliage has peaked. You can also recognize maples by their large, distinctive leaves.
Method 3 of 4: Recognizing Acorns
Step 1. Understand the function of the acorn
It contains the "seeds" of the tree and, if planted in the right place, it could even sprout and turn into a massive oak.
- Acorns develop within a cup-like structure called a dome; its function is to supply the nutrients that come from the roots, from the leaves and that go through the whole tree, branches and stems, until they reach the inside of the acorn. Looking at the acorn with the tip down, the dome resembles a hat on top of a walnut; technically, it's not part of the acorn, but it's more of a protective coating.
- Each acorn typically contains one oak seed, although there may sometimes be two or three. An acorn needs six to eighteen months to mature into an oak seedling; it is more likely to germinate in humid environments (but not too much) and grows when activated naturally by the freezing temperatures of the Northern Hemisphere winter.
- Acorns have evolved to attract deer, squirrels, and other woodland creatures to eat them. When the animals then excrete the feces in the woods, they also spread the small oak seeds. When they release the digested seeds - or, as is the case with squirrels, compulsively hiding the acorns and then forgetting them in the spring - the animals sprinkle them throughout the ecosystem. Most of the seed does not survive and does not develop into a mature tree, but the one that manages to overcome the difficulties of nature produces acorns in turn.
- When the acorn falls to the ground, there is about a one in 10,000 chance it could become a fully grown oak tree - that's why the tree has to produce so many!
Step 2. Look at them on the branches or around the base of the trunk
Acorns come in different colors and sizes, but most of them have the classic rough "hat" with a smooth, pointed base. The size data described below helps to gather more information about the tree:
- Inspect the stem the acorn is attached to, take note of its length and how many acorns it produces.
- See what the dome looks like. The fruit grows from this woody coating that resembles a head wearing a hat. The domes may be covered with scales and show wart-like formations that take on the appearance of a fringe; in other cases, they are characterized by colored decorative motifs, such as concentric circles.
Step 3. Measure the length and diameter of the fruit
Some species produce long acorns, in other cases they are more squat or almost spherical; also take note of the portion covered by the dome.
- Generally speaking, mature red oak acorns are slightly larger; they are 18-25 mm long and the dome occupies ¼ of the length.
- The fully developed acorns of white oaks tend to be smaller: they range from 12 to 18 mm.
Step 4. Look at its features
Take note of the color of the acorn, if it has a pointed end, and if it shows other features such as ridges or stripes.
- Those of red oak tend to be of a more intense reddish-brown color, while those of white oak take on grayish and pale shades.
- Trees belonging to the white oak group produce acorns within a year; these contain less tannins and taste better for woodland creatures - deer, birds and rodents - but grow sporadically from year to year.
- Trees in the red oak group take two years to develop mature acorns, but they reproduce annually and are capable of providing a steady harvest over time. Although these acorns are richer in tannins and, in theory, are "less flavorful", this feature does not seem to discourage woodland animals from eating every oak fruit they encounter.
- Red oak acorns typically contain large amounts of fat and carbohydrates, but white oak acorns are the richest in carbohydrates.
Method 4 of 4: Recognize Wood and Bark
Step 1. Look at the cortex
Look for a tree with a trunk covered with a hard, gray bark with deep grooves and ridges.
- The furrows and raised areas often join in gray and flat areas on the largest branches and on the main trunk.
- The color varies between the different species, but is almost always of a gray hue; some oaks have a very dark, almost black bark, while others have a color close to white.
Step 2. Consider the size of the tree
The old oaks, in particular, stand out for their impressive size and, in certain areas, these behemoths dominate the landscape - as in the "Golden Hills" region of California.
- Oak trees grow quite large and rounded at a height of 30m or more. These are lush and well balanced trees and it is not uncommon for the diameter (including foliage and branches) to be equal to the height.
- The trunks can be very thick, some species usually reach a circumference equal to or greater than 9 m; these trees can live over 200 years - there are some that are over 1000 years old. Generally, the thicker the trunk, the older the tree.
- Oaks have quite large canopy, which is why they are known to provide shade and coziness during the summer months.
Step 3. Recognize the wood once it has been cut
If the tree has already been felled, cut and divided, then evaluate some characteristics, such as the color, smell and appearance of the veins.
- Oak provides one of the hardest woods and this feature is why it is so popular for building furniture, flooring and household items. Dry logs are sold as firewood, as they burn slowly and completely.
- Remember that there are many species of oaks, so it is important to know where the tree was felled; if you don't know where the wood comes from, you can only tell if it is white or red oak. This distinction is useful for most non-scientific purposes.
- Red oak wood has a reddish hue that becomes more intense as the tree dries up; white oak wood is lighter.
- Oak wood is often confused with maple wood, but you can distinguish one from the other by smell; the maple one has a sweeter scent and in fact it is from the latter that the syrup is extracted, while the oak one has a more intense and smoky aroma.
