The Oaks of the genus Quercus account for more tree biomass than any other species in North America and Mexico (1). Northern Pin Oak is a native deciduous tree with a short trunk, many small branches and a narrow to rounded crown, usually growing in Minnesota to 50 feet in height and to 2 feet in diameter. The lower part of the trunk will often have old branch stubs. Young trees will be more narrow, mature trees can develop the rounded crown if they are not crowded. The largest known specimen in Minnesota (as of 2019) is Houston County, measuring 97 feet high, 68 foot crown spread and 143 inches in circumference with a ranking of 257 points. There is no entry in the national registry for a Northern Pin Oak (as of 2020).
The bark is gray or dark brown, smooth initially, becoming shallowly fissured and furrowed into shallow grooves and narrow plates. The inner bark is light yellow to orangish. Twigs have light color lenticels. Terminal buds are a dark reddish-brown, but silvery or tawny near the tip, often 5-angled in cross section. Clusters of buds are located at the tips of the twigs.
Leaves are alternate, 3 to 5 inches long and 3 to 4 inches wide, elliptical, broadest across the lobes nearest the tip, and can be indented over half way to the mid-vein with 5 to 7 deep lobes (sometimes 9). Most lobes go halfway to the mid-vein. Each lobe ends in several bristle-tipped teeth (awns). The area between the lobes (the sinuses) is generally round. As with most oaks, leaf shapes can be quite variable. The leaf base can vary from obtuse to truncate. There is a short leaf stalk, a shiny green upper surface, lighter color under with tufts of hair along the mid-vein. The branching secondary veins appear raised from the surface. Fall color can vary from brown to a deep red turning to brown.
Flowers: The tree is monoecious, that is with separate male and female flowers. The male flowers develop as hanging catkins from the leaf axils of last years' growth. Each male flower has six stamens (can very from 2 to 12), which have long spreading white filaments when the flower fully opens. The female flowers are more reddish-green and appear as small slender spikes in the axils of new growth. They have 3 (to 6) carpels and styles that are slender and short. There are no petals; both sexes have the sepals are fused together. Both develop as the leaves open.
Seed: The female flowers mature to an egg-shaped acorn, rarely subglobose in shape, 1/2 to 1 inch long, 1/3 to 1/2 enclosed in a deep cup to top-shaped cap with tightly pressed scales which are finely hairy and have straight or slightly concave margins. The cap tapers abruptly to a stalked base. Caps do not expand as the acorn grows longer. The nut is reddish-brown. The acorn matures in the second summer as do most species in the Quercus Sect. Lobatae - the Red Oak Group. The top of the nut may occasionally have a faint ring of fine pits at the apex. Dispersion is by animals in August to December of the second year. Trees require some age before bearing - upwards of 20 years.
Habitat: Northern Pin Oak grows from a deep taproot with widespread lateral roots and will re-sprout from a root collar or stump. It prefers upland sandy soils and is very drought tolerant. Like the Red Oak, this species is susceptible to Oak Wilt Disease and therefore should not be pruned during the growing months of April to September.
Names: The genus name, Quercus, is the Latin word for Oak. The species, ellipsoidalis, means elliptic and refers to the leaf shape. The author name for the plant classification from 1899, ‘E.J.Hill.” is for Ellsworth Jerome Hill (1833-1917) American Botanist who published extensively on trees and herbaceous plants of the central United States, including several papers on Quercus ellipsoidalis. Although a graduate of Union Theological Seminary in New York City, he was largely self-taught in botany.
Comparisons: The proper common name for this plant is Northern Pin Oak to prevent confusion with the similar Pin Oak, Q. palustris, which is a more southern plant and not native to Minnesota. There are no other oaks in Minnesota in the wild that have a leaf like this, but the tree can hybridize with the Red Oak, Q. rubra, but Red Oak leaves are not shiny and the lobes are less deeply cut. In other areas a closely resembling tree is the Scarlet Oak, Q. coccinea, where the acorn cup is turbinate to hemispheric, scales with broad glossy base, scale margins often strongly concave; nut ovoid to subglobose, with 1 or more concentric rings of pits at apex.
Check the Oak Leaf Comparison Sheet.
Above: 1st photo - Northern Pin Oak has many short branches and a narrow to rounded crown - more narrow when young as this specimen shows. 2nd photo - bark of a young tree. 3rd photo - Bark of older trees is shallowly fissured and furrowed into shallow grooves and narrow plates.
Below: The terminal bud is usually 5 sided in cross section, dark reddish-brown.
below: Northern Pin Oak leaves are quite variable. Here are 3 examples of N. Pin Oak from the same tree. They are broadest across the central lobes; lobe sinuses are round; lobes end in bristle teeth.
Below: 1st photo - The fall color of the leaves. 2nd photo - The underside of the leaf is paler color showing the fine vein pattern. 3rd photo - An example of a mature tree growing in an uncrowded habitat which has allowed it to develop a rounded crown.
Below: Drooping male flower catkins rise from the leaf buds of last years growth. 1st photo - as they are forming. 2nd photo - as they have elongated and release pollen. 3rd photo - Female flowers rising from the leaf axils of new growth.
Below: 1st photo - A section of new growth rising from last years twig. The female flowers are just forming in the leaf axil in the upper right corner of the photo. 2nd photo - Newly formed acorns.
Below 1st photo Maturing green acorns in the second summer. Acorns have a deep top-shaped cap with tightly pressed scales tapering abruptly to a stalked base. 2nd photo The nut is reddish-brown at maturity.
(1) Ascent of the Oaks, Hipp, Manos, Cavender-Bares, SA, Aug 2020.
Northern Pin Oak is indigenous to the Garden. Eloise Butler catalogued it on April 29, 1907. It has a rather restricted native range, being found only in central U.S. states of ND, MN, IA, IL, MO, WI, MI, OH and IN. In Canada it is known only from Ontario. Within Minnesota it is widespread, found in over 2/3rds of the state with most exceptions being counties in the SW quadrant and a few elsewhere. It is the most common oak on the sandy soils of north central Minnesota.
There are six species of Oak generally found in parts of Minnesota that are not considered hybrids or rarities that have not been collected in the last 100 years. These are: White Oak, Q. alba; Swamp White Oak, Q. bicolor; Northern Pin Oak, Q. ellipsoidalis; Bur Oak, Q. macrocarpa; Northern Red Oak, Q. rubra. and Black Oak, Q. velutina. Chinkapin Oak (Chestnut Oak, or Yellow Oak), Q. muhlenbergii was native but is historical only now, last collected in 1899; Scarlet Oak, Quercus coccinea, can also grow here as can Pin Oak, Quercus palustris, but neither are native.
Uses: Northern Pin Oak is valuable for its wood, used for cabinetry, flooring and finish lumber. It is marketed as Red Oak. The acorns are edible although bitter and with more tannin than the White Oak group. Bitterness is removed by leaching and the tannin by boiling. Native Americans made use of most acorns for acorn-flour. Fernald (Ref. #6) has some detail on how this was done.
It is difficult visually to separate the species of the Red Oak group when you are looking a piece of lumber. As a general characteristic the Red Oak group has wood with the tallest rays less than 1 inch and the latewood pores are few and distinct. Whereas, in the White Oaks the tallest of the largest rays are greater than 1-1/4 inches and the latewood has numerous small pores that grade into invisibility. A small hand lens is necessary to do this.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"