Oaks occur in a wide variety of habitats. Some species of the Eastern Deciduous Forest are large, stately trees occurring in forests with rich, moist soils. Others are specialized for dry conditions such as rocky or limestone soils. A few species are most commonly found along the margins or ponds, streams, and swamps. Outside of the Eastern Deciduous Forest, oaks grow along streams in the prairie, in the drier parts of the Montane Forests of the western United States, and are common in the dry mountain regions of the southwest.
Oaks are also among the dominant trees of the Chaparral region of California.
The white oaks are recognized by the rounded lobes of the leaves such as the leaf shown in the bottom picture on the left. The acorns of the white oaks are not strongly bitter in taste because of low levels of tannins. Most species of White Oaks are found in the Eastern Deciduous Forest, although some species occur on the Pacific Coast, and one is a dominant tree of the Rocky Mountains. Technically the red oak group contains the live oaks as well, but because the two groups are so distinct they are separated here. The red oaks are bitter in taste with high levels of tannins.