The White Oaks
As many characteristics as possible, from leaves to location, must be taken into consideration when identifying oak trees.
Missouri is over 30 percent forested, and oaks are among out most important and abundant trees. Oaks provide food for wild animals in the form of acorns, especially for deer, wild turkeys and squirrels. Oaks belong to the so-called hardwood trees, in contrast to the conebearing needle trees, and are a most important source for lumber. The lumber we cut from oak trees is important to Missouri's economy, it is used for making barrels, furniture, cabinets and flooring.
Oaks also shape the landscape of much of Missouri, provide shade to homes and streets and serve as historical markers.
The oaks form a large group (genus) of worldwide distribution. Most are trees but some are shrubs. One estimate calls for 450 species in the world; another, more modest, calls for 275. In North America, north of Mexico, there are about 54 species, for which 21 are growing wild in Missouri.
This abundance of American oak species compares with just three to five in all of Europe. When the glaciers covered much of the northern hemisphere during the last two million years, our oak species found favorable conditions further south; were trapped by mountain ranges lying east to west, blocking their growth to the south.
Problems of Identification
To begin with, oaks hybridize readily. While one speaks commonly of "hybrid sterility," our oaks have viable hybrids—hybrids with seeds that produce trees.
The amazing variability in the leaf shapes of certain species is confusing. This forces us to accept certain basic leaf shapes for identification, though we know full well that differing shapes are common.
The leaves of young trees often vary totally from the mature shape. They can be huge, an assist by nature to form an enlarged chlorophyll factory, but not conducive to identification.
No wonder Julian Steyermark, author of Flora of Missouri, said that in identifying oaks, it must be kept in mind that as many characteristics as possible–leaves, twigs, winter buds, range, bark, site–must be taken into consideration.
Oak Characteristics
Oaks have separate male and female flowers on the same tree. Male flowers are pollen-bearing stamens on catkins; females are rounded-to-pointed, knoblike and usually on short spikes in leaf axils. Pollination is by wind, requiring huge amounts of pollen.
The fruit, the acorn, takes one or two years to reach maturity. The combined fruits of oaks, hickories, walnuts and beeches form the "mast" of life, sustaining deer, raccoon, squirrels, chipmunks,'possum, mice and fox. Turkey and quail also eat acorns, as do waterfowl.
Acorns are attacked by a host of insects; because of that, only an occasional one will produce a new tree. Most oaks take more than 30 years before they produce acorns.
The following is an attempt to provide useful information for identifying native oaks. In no way is this a botanical text, which would have to cover a much greater area in much more detail. The native oaks are presented in two groups, the white oaks and the red oaks.
White Oaks–General Characteristics:
- produce the most valuable oak lumber, because the cells contain bubblelike structures–tyloses–making the heavy wood leakproof.
- acorns mature during one year.
- the cups of acorns contain no hair inside.
- leaves are lobed or serrated (saw toothed without bristles.)
- produce "sweet mast," having less tannin than the red oaks.
Key ID Features: Scaly, light colored bark on upper limbs; warty scales on acorn.
White Oaks
White Oak (Quercus alba) - The most important hardwood lumber tree in the United States and Missouri, setting the standard of lumber for all other oaks. Grows in either dry or moist situations, but not in wet ones. Height to 100 feet tall throughout Missouri, with heavy, often nearly horizontal branches; wide-spreading.
- Leaves: With five to seven rounded lobes in two distinct forms: one has shallow, wide, rounded lobes; the other has long, narrower, fingerlike lobes with indentations nearly to midrib of leaf.
- Bark: Light gray; rough with long loose scales; becoming blocky on very old trees.
- Acorns: About 3/4-inch long with a cup covered by warty scales.
- Wood: Of great importance for whiskey barrels and barrels staves.
The name alba is Latin for "white."
Key ID Features: Leathery cross shaped leaves; light brown bark with scaly ridges
Post Oak (Quercus stellata) - Grows in dry and rocky upland woods, to 60 feet tall. Characteristics similar to white oak. Although it is found in nearly every county of the state, it is most common in the Ozarks.
- Leaves: Usually with five lobes, two of which, above the middle of the leaf, are broad, forming a cross with the axis of the leaf. These and the top lobe are normally slightly indented.
- Bark: Light brown; divided by deep fissures and scaly ridges.
- Acorns: Small to 3/4-inch long, the cup overs one-third to one-half of the nut.
The name post oak indicates that the wood used to made into fence posts.
The Latin Stellata means "star," referring to the starlike tufts of hair on the surfaces of the leaf.
Key ID Features: Bark in vertical ridges; large distinctive acorn; corky, thick twigs.
Bur Oak (Quercus macrocarpa) - Grows both on upland and lowland sites, but does best on rich, moist soils; to 120 feet tall, throughout Missouri.
- Leaves: The largest of any native oak, to one foot long and very wide. Two different basic shapes exist: one widest above the middle, the upper portion shallowly lobed, the lower lobes longer. The other has a deeply lobed central section with indentations coming close to the central vein and a narrower upper part, but still wider than the lower lobes,. Both forms are found on the same tree.
- Bark: Similar to white oak but darker and more vertically ridged.
- Acorns: The largest of all North American oaks, about 1 ½ inches in diameter, surrounded by a deep cup, which is scaly and has a hairy fringe at the rim. Squirrels are specially fond of them.
Macrocarpa is Greek for "big-fruited."
Key ID Features: Peeling bark on twigs; long stem on acorn.
Swamp White Oak (Quercus bicolor) - A medium-sized oak of moist bottomlands, growing sparsely in the northern two-thirds of Missouri, but also found in the Ozarks.
- Leaves: Shiny, green above, downy-white below, with many shallow, evenly spaced lobes all along the egg-shaped leaf, which is widest near the middle of the leaf.
- Bark: Bark on the upper limbs and twigs peels off in papery scales; dark brown and deeply fissured on the main stem of old trees.
- Acorns: Usually carried in pairs, characteristically on a long stem 2 ½ inches long, the cup scaly and with fine, wooly hair.
Bicolor, Latin"two-colored," referring to the leaves.
Key ID Features: Ashy gray bark with thin flakes; usually found growing on limestone based soils and glades.
Chinkapin Oak (Quercus muehlenbergii) - (also known as chestnut oak; Steyermark: Q. prinoides). Grows both on dry, rocky uplands and moist bottomlands throughout Missouri, to 100 feet tall.
- Leaves: Coarsely serrated (like saw teeth) along entire margin, either narrow or wide oblong, wider above the middle, ending in a pointed tooth (but no bristles).
- Bark: Ashy gray; rough and flaky
- Acorns: Small, to 3/4-inch long, dark chestnut colored, the cup usually with a short fringe, covering one-third to one-half of the nut.
Chinkapin is the name of a shrubby chestnut, which has leaves similar to this oak.
Muehlenbergii (often misspelled) for the botanist Gotthilf Henry Ernest Muehlenberg, 1753-1815.
Key ID Features: Only found in Southesast Missouri in low wet areas; large acorn with pointed scales.
Swamp Chestnut Oak (Quercus michauxii) - (also know as cow-oak or basket oak). Restricted to southeast Missouri where it is found in moist soils in low, wet woods and along streams; to 100 feet tall.
- Leaves: Similar to chinkapin oak but the small serrations (lobes are rounded, not toothed. Only the tip of the leaf is pointed. Leaf is egg-shaped with the broadest part above the middle.
- Bark: Light gray or tan, irregularly furrowed or scaly.
- Acorns: Large, to 1 ½-inches long, the cup with pointed scales and matted silky hair. The acorn is quite low in tannin, and thus called "sweet." It is known as chestnut oak because the leaf resembles that of a true chestnut (Castanea).
Michauxii for the French naturalist Andre Michaux, sent by his government to the U.S. to collect plants, 1746-1802.
Key ID Features: Acorn neatly enclosed by cup; usually found in swamps of Southeast Missouri.
Overcup Oak (Quercus lyrata)
- Leaves: Lobed with irregular broad lobes of varying depths. Leaf is dark green and shiny above; light green and hairy beneath.
- Bark: Brownish-gray and rough; with large irregular plates or ridges.
- Acorns: Up to 1-inch in diameter; almost entirely enclosed in a deep, unfringed cup.
Restricted to southeast bottomlands and a few localities in east-central Missouri.
Key ID Features: Low shrub 3-10 feet tall; only found in western half of state; leaves have fewer and more blunt lobes than chinkapin oak.
Dwarf Chestnut Oak (Quercus prinoides) - (also know as dwarf chinkapin or scrub oak). Grows as a multi-stemmed shrub only a few feet tall or as a small tree Usually found in prairies and open areas of north Missouri.
- Leaves: Similar to those of chinkapin oak but smaller and usually with more blunt lobes. Leaf is green above, lighter-colored and hairy beneath.
- Bark: Brownish-gray becoming rough or scaly on older wood.
- Acorns: About ½-inch in diameter with small, warty scales on cup. This is the shortest of Missouri's oaks, and it can produce abundant acorns although only 3 to 10 feet tall
