Pin oak is a member of the broad red oak group (red, black, blackjack, pin, northern pin, and shingle oaks). This group is characterized by having bristles or points on the leaf lobes and acorns which mature in two growing seasons and sprout in the spring after maturity. 

Pin oak has leaves 3 to 6 inches long, bristle tipped, deeply 5 to 7 lobed with wide circular or U-shaped sinuses. The leaves are smaller and the lobes are deeper than red oak and have fewer lobes than black oak. The leaves are dark green on the upper surface, and paler below with tufts of pale hairs in the axils of the veins. The twigs are slender, smooth, green to red brown in color. Buds are 1/8 inch long, red-brown, shiny, sharp-pointed, and angled. Acorns are hemisphere shaped, light brown, striped with dark vertical lines in a cup covering only the base of the acorn with appressed, free-tipped scales. The bark on the lower trunk is gray brown and slightly ridged; on smaller trees it is smooth and light gray to brown. 

Pin oak is a bottomland species, preferring moist, acidic soils. It is native in the southeast part of Iowa along the Mississippi River and its tributaries. It attains heights of 70 to 80 feet, with a spread of 25 to 40 feet. It has strong apical dominance, often developing into a tree with a single main leader with the upper branches pointing up and the lower branches pointing down. It is a poor self pruner, holding its branches longer than most other oaks. 

Pin oak has been planted throughout Iowa as a ornamental because of its ease of transplanting, handsome foliage, and pyramidal crown. However, pin oak is very site sensitive; it prefers moist, acidic sites. On sites which are not acidic, it often exhibits iron chlorosis, a yellowing of the leaf tissue between the veins. This is due to iron deficiency because of the low availability of iron in higher pH soils. It should not be planted on sites with a soil pH above 7.0 to 7.3. 

The wood of pin oak is heavy, hard and usually knotty. It is similar to red oak, but of lower quality, and has the same uses as other red oaks.

Where can you get information?--Contact Paul H. Wray at (515) 294-1168 or write:

Native Trees of Iowa
ISU Forestry Extension
Department of Natural Resource Ecology and Management
339 Science II
Ames, Iowa 50011-32211