Quercus ellipsoidalis (Northern Pin Oak)
|Also known as:|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; heavier, well drained soil; forest|
|Bloom season:||mid May|
|Plant height:||over 100 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Male and female flowers are borne separately on the same branch, the males on 1½ to 4 inch long green, string-like clusters (called catkins) from bud clusters at the tip of the previous season's growth. 1 to 3 female flowers, with bright red styles and a short, stubby, green stalk, sit in the leaf axils of new growth.
Leaves and bark:
Leaves are simple and alternate, the blade oval or elliptic to nearly round in outline, 2¾ to 5½ inches long and almost as wide on a ¾ to 1¾ inch stalk. Each side has 2 to 4 primary, finger-like lobes, each with 2 to 5, sharply pointed secondary lobes at their tips. The sinuses between the lobes are more often broad and rounded, extending over half way or nearly to the central vein. Upper surface is deep green and glossy, the lower surface dull, light green with patches of fine hair where the lateral veins diverge from the central vein. Their fall color is typically more often deep maroon to rusty red, though on occasion can be brilliant scarlet tinged, all however turning a dull, light brown later in the season, often persisting until spring bud break (marcescent).
Bark on mature trees is dark brown to gray with blocky ridges and moderate to deep vertical furrows. In closed canopy forests it is tall and straight with few or no lower branches, but in more open areas, lower branches grow downward creating a large round crown, often close to the ground. Twigs are reddish brown, often glossy.
Northern Pin Oak is considered a medium sized tree and rarely attains the over all stature of our native white oak species. However the record pin oak for Minnesota reached 95 feet in height and was nearly 4½ feet diameter at breast height, but due to its age and advanced heart rot, succumbed to a wind storm a few years ago. A common oak species throughout central and southeastern Minnesota, it is noted for its tolerance of dry, sandy or rocky soils associated with savanna and dry prairie margins and is highly fire adapted as well. It can also be found in more mesic wooded uplands which is the preferred habitat of Northern Red Oak (Quercus rubra), with which it is often confused. They share many over lapping characteristics and can be a challenge to distinguish by even well trained foresters. The best identifiers are Pin Oak's shiny upper leaf surface combined with typically deeper, broader, rounded leaf sinuses, its small, ellipsoid shaped acorn and its deep cap. Immature acorns are also frequently visibly striped with darker bands. It can also very difficult to distinguish from Black Oak (Q. velutina), which is perhaps even more tolerant of dry sandy soils, though their ranges only overlap in Minnesota's extreme southeastern counties. While Black Oak's leaves are also shiny on the upper surface, they tend to have more squarish lobes and often have fine, fuzzy hairs across the lower leaf surface that rub off easily to the touch. Black Oak acorns also tend to be rounder and the cap typically covers 50% or more of the nut.
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- Northern Pin Oak tree
- fall color
- Northern Pin Oak buds and bud scars
- more leaves
- leaves with very deep sinuses
- compare Red Oak and Pin Oak leaves
Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka and Ramsey counties.
Have you seen this plant in Minnesota, or have any other comments about it?