Those Oaks with pointed lobes are in the Red Oak or Black Oak group and those with rounded lobes are in the White Oak group. The namesake species for these two groups are common throughout our area where Oaks are to be found: Quercus rubra or Red Oak and Quercus alba or White Oak. Oak forests are dominant throughout our region, but are characteristic of certain areas.
It is not uncommon for parents to tell their children that acorns are poisonous. This is sometimes due to lack of knowledge and sometimes simply to discourage kids from eating them. In ancient times, however, people in or near Oak forests would definitely be eating acorns. Many cultures even depended on acorns as dietary staples.
Native Americans throughout the country (as Oak trees are common in many parts of the nation) depended on acorns as food. Since most species contain a large amount of tannic acid, they are most often prepared by leaching. Leaching tannins can be done in cold water or hot. Native Americans would often use streams and other natural bodies of water to leach their acorns. Modern approaches often utilize tap water.
Whether outside or in, the method is basically to soak the acorns in water, changing the water when it becomes dark and astringent (a couple times a day) until the acorns are mild to taste. Since tannins are distinctly astringent (dry and constricting) and bitter their presence is easily detectable with a nibble.
Tannins are not overtly toxic. Like many “toxins” it is a matter of dose. Many people have consumed more Oak tannins than they realize, for the astringency of a dry wine comes not only from the grapes but from the Oak wood that wine barrels are made from (or, in modern times, from the oak woodchips added to simulate the effect of aging in an Oak barrel). So even if you have not tried acorns yet, you likely have “eaten” some Oak along with a recent dinner!
Tannins in high amounts are washed away as unwanted constituents, but often we want tannins for medicinal purposes. The drying, constricting, anti-inflammatory properties of Oaks and many other plants that contain tannins are very useful for disorders of the skin, digestive tract, and cardiovascular system. Particularly people who live close to nature, such as pre-colonial Native Americans would find use for tannin-rich herbs in the treatment of rashes, cuts, wounds, bites, and stings. Additionally, sore throats and digestive problems can often be remedied with astringent herbs. When the acorns are not available, the bark and leaves were used as a source of tannins.