The Pin oak (Quercus palustris) is an oak in the red oak section Quercus sect. Lobatae. It is mainly native to the eastern United States, from Connecticut west to eastern Kansas, and south to North Carolina across to eastern Oklahoma. It is also native in the extreme south of Ontario, Canada. It is naturally a wetland tree, and develops a shallow, fibrous root system, unlike many oaks, which have a strong, deep taproot when young. It is confined to acidic soils, and does not tolerate limestone. The specific name palustris means "of swamps".

The Pin oak is broad conic when young, with numerous small branches radiating out from a central leader. When older, some upper branches become quite large and the central leader is lost, while lower branches gradually die out. The name "pin" is due to the many small, slender twigs. The Pin oak is not a long-lived tree, usually living only 90 to 120 years. The leaves are 7-15 cm long and 5-10 cm broad, lobed, with five or seven lobes, and deep sinuses between the lobes. Each lobe has 5-7 bristle-tipped teeth. The leaf is mostly hairless, except for a very characteristic tuft of pale orange-brown down where each lobe vein joins the central vein. The acorns, borne in a shallow cup, are hemispherical, 10-14 mm long, green maturing pale brown about 18 months after pollination; the kernel is very bitter.

Uses

Pin oak is one of the most popular landscaping trees in the United States. The fibrous root system makes it easy to transplant. However, because the tree is adapted for wet, acid soils, it may suffer a condition called iron chlorosis, in which the foliage yellows, when planted in drier, alkaline, and iron-poor soils. The wood from this tree is generally marketed as Red oak, but is of significantly inferior quality, being somewhat weaker, often with many small knots.