Quercus macrocarpa

The bur oak, known scientifically as Quercus macrocarpa, is a massive deciduous tree. It is native to central and eastern North America. This species belongs to the white oak section, which is called Quercus sect. Quercus. You might also hear it called the mossycup oak or the scrub oak. The name macrocarpa comes from Ancient Greek words meaning "large fruit." This refers to its most famous feature: its acorns. These acorns are the largest of any oak tree in North America. Because they provide so much food, they are vital to many ecosystems.

Growing into a giant takes a long time for this species. It is one of the slowest-growing oaks in existence. When the trees are young, they may grow only 0.3 cm per year. However, a well-established tree can grow up to 60 cm every year. In full sun, a 20-year-old tree might reach 10 meters in height. Mature trees can reach 20 meters, and sometimes even 30 meters tall. Their trunks are incredibly thick, reaching diameters of up to 1.5 meters. Most bur oaks live between 200 and 300 years. Some individuals may even live for 400 years.

The physical structure of the tree is very distinct. The bark is gray and features deep, vertical ridges. Its leaves are long and broad with lobed margins. Usually, the bottom two-thirds of the leaf is narrow and deeply lobed. The top third is wider and has shallow lobes or large teeth. In the spring, the tree produces greenish-yellow flowers called catkins. The acorns are long and broad with a very large cup. This cup wraps around much of the nut and has overlapping scales. Often, the edge of this cup has a small fringe.

Bur oaks are very widespread across the continent. They grow from New Brunswick in Canada down to North Carolina. Their range extends west to Alberta, Montana, Wyoming, and New Mexico. Most populations live in the Great Lakes region and the Mississippi-Missouri-Ohio Valley. This tree grows farther north than any other North American oak. It prefers temperate climates and open areas rather than dense forests. It is often found on eastern prairies near waterways. The tree is highly drought resistant. This is likely due to a long taproot that grows deep into the soil.

This tree has a unique way of surviving in the wild. In the Midwest, they often live in oak savannas. These areas frequently experience fires in the spring or fall. Bur oaks older than 12 years are fire-tolerant because of their thick bark. Without these fires, other shade-tolerant trees might take over. The tree also uses a survival strategy called masting. This means the tree produces heavy acorn crops only every few years. This massive amount of food overwhelms the animals that try to eat them. This ensures that enough seeds survive to grow into new trees.

Many different animals rely on the bur oak for survival. American black bears sometimes tear off branches to reach the acorns. Deer and porcupines eat the leaves, twigs, and bark. The tree is also a home for many tiny creatures. It is the only known host plant for Bucculatrix recognita caterpillars. Many species of arthropods, such as mites and wasps, create galls on the leaves. A gall is a small bump formed on the plant. Various species of cynipid wasps are known to do this.

Humans have found many uses for the bur oak throughout history. The wood is very durable and commercially valuable. It is used to make flooring, cabinets, fence posts, and barrels. Native Americans used the astringent bark to treat wounds, rashes, and diarrhea. The acorns can even be eaten if they are boiled or eaten raw. Today, nurseries plant them in gardens, parks, and even on urban sidewalks. They are hardy enough to grow from Alaska to Texas. Even the wood tells a story, as the annual rings show the tree's growth history.