Oak trees are in our poems, songs and legends. These botanical treasures inspire us with their longevity and beauty. With their tall trunks and wide crowns, these majestic trees provide shade and habitat. Many survive for 300 years and some live as long as 1,000 years. The best part is, there are many varieties of oak trees for you to plant and identify on walks through parks and forests.
Oaks are part of the Quercus genus, and there are about 600 species. Native to the northern hemisphere, oak meadows can be valuable habitats for wildlife. Oak trees are part of a complex ecosystem. In many parts of Europe and North America, acorns are used to feed livestock. The Roman poet Virgil once wrote, "Full in the midst of his own strength he stands, stretching his brawny arms and leafy hands." The oak tree is America's official National Tree. There are about 60 varieties of oak trees in North America. Most are red or white oaks.
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The group of "red oaks" includes trees that are usually tall and sturdy with reddish brown, ridged bark. Red oaks have leaves with pointed lobes and small bristles at the tip. Trunks typically grow to about 3 to 3.5 feet wide. Red oaks grow faster than white oaks. Acorns of red oaks take two years to mature. The acorns sprout the next spring after they drop to the ground. Common red oaks include willow oak (Quercus phellos, USDA zones 5-9), black oak (Quercus velutina, USDA zones 3-9), Japanese evergreen oak (Quercus acuta, USDA zones 9-11), water oak (Quercus nigra, USDA zones 6-9) and pin oak (Quercus palustris, USDA zones 4-8).
Yes, a black oak is actually in the family of red oaks. Black oak trees have smooth, gray bark and its leaves turn bright red in the fall.
Willow oaks have thin, straight leaves, resembling those of a willow tree. Its acorns are not as messy as others. The tree also adapts well to urban conditions, so it makes a nice street tree or as a buffer along highways. Willow oaks grow 60 to 75 feet tall. They transplant well when dormant in the winter.
Japanese evergreen oaks are smaller than other oak trees, topping out at 20 to 30 feet tall with a width of 20 feet. These oaks prefer the warm, coastal Southeast, but they will grow inland in protected areas. Despite its size, it makes for a nice shade tree. Its growth is shrubby and it can make a nice lawn tree or screen tree.
Pin oaks make a nice shade tree. These trees grow 60 to 75 feet tall, and they grow nice and straight, with a well-shaped canopy.
White oaks have a light gray bark and trunks that grow up to 4 feet wide. The leaves of white oaks are lobed with round edges. Although their leaves turn red or brown in the fall, white oaks keep their leaves in winter long after most trees have shed their leaves and often don't drop off until spring. Acorns mature after a year, and these trees sprout soon after falling to the ground. Varieties include chinkapin, post oak, bur oak and white oak.
Within the white oak group is the white oak species (Quercus alba, USDA zones 3-9). This is a slow-growing shade tree that grows well near water, although it adapts to most conditions. After 10 to 12 years, this tree will only be 10 to 15 feet tall. But one day, it will be 50 feet high. It should be planted in an area where there is plenty of room for it to spread. It should not be near sidewalks or patios because the trunk will flair at its base. Prune this tree in the winter when it's dormant.
The bur oak (Quercus macrocarpa, USDA zones 3-8) is another large shade tree that grows 70 to 80 feet tall. Its corduroy-style, furrowed bark makes it easy to recognize. This oak will be found further north and west than other oaks.
Live oaks (Quercus virginiana, USDA zones 8-10) are evergreen oaks that live all across the southern United States. A large, spreading tree, it prefers rich, coastal soils and the banks of streams and rivers. Live oaks are often seen draped in Spanish moss and bring to mind images of southern weddings and historic small towns.
Oak Tree Diseases
Wet, cool summers can bring on oak anthracnose – a fungal pathogen – to many oak varieties. Symptoms include small brown spots and irregular dead areas on distorted leaves, but it typically doesn't cause much leaf drop.
Bacterial leaf scorch is caused by a bacterium and its symptoms appear in late summer through fall. Symptoms are most severe in dry summers because the bacterium blocks the water-conducting vessels that move water from the roots to the leaves. Trees with this disease have scattered yellowing and browning of leaf margins throughout the canopy. Leaves usually remain on the tree until they drop in the fall.
Oak wilt is caused by a fungal pathogen. It causes a vascular infection, blocking the water and nutrient circulatory system the tree depends on. Symptoms show on red, scarlet, black and pin oaks. It is spread by root grafts, so it affects trees in close proximity. It can also be spread by beetles feeding on the sap. Symptoms usually appear in spring and early summer near the top of the tree. There is often extensive leaf drop by mid-summer.
The Oak Tree in Legend
The oak tree has a strong presence in mythology, and early Europeans venerated oak trees. Ancient kings wore crowns of oak leaves, and oak leaves are still symbolic of military prowess. Because of their size and longevity, oaks are symbols of honor, nobility and wisdom.
Many early European churches were built with oak boards. Later, many parishes adopted an oak to be the "Gospel Oak," and springtime ceremonies would take place beneath it.
Plant oak trees where they'll have a lot of room to grow. Oaks like full sun and can adapt to most soil conditions. A good rule of thumb is to give an oak space to grow 80 feet tall and 80 feet wide.