Black Oak is a native deciduous tree growing 50 to 80 feet tall with an irregular open spreading crown. It is a member of the Quercus Sect. Lobatae - which contains all species of the Red Oak Group.
The bark is gray and smooth on young trunks, becoming blackish, thick and rough and deeply furrowed into ridges that have horizontal breaks. The inner bark is yellow to orange and very bitter.
Twigs are stout and grayish green to reddish-brown in color, with many small lenticels, usually smooth but new twigs may have surface hair. The buds are large, buff in color, with fuzzy hair, and jut out at angles from the twig. Terminal buds have 5 angles in cross-section.
The leaves are elliptical, long stalked, usually with 5 to 9 (5 usually) lobes that are either shallow or deep and narrow. Lobes end with a few bristle-tipped teeth (awns) of which there can be 15 to 50. The leaf base can be obtuse to truncate in shape and is usually a bit unequal from side to side. The upper surface is shiny dark green and the underside a pale green with some brown hairs along the main veins. The secondary veins appear raised on both surfaces. Fall color is brown to dull red.
Flowers: The tree is monoecious, that is with separate male and female flowers. Male flowers occur in yellow-green 2 to 4 inch hanging catkins from the leaf axils of last year's growth. Female flowers are on short stub spikes, containing 2 to many flowers, emerging from the leaf axils on new growth. They are reddish-green. Both appear with the leaves.
Fruit: Female flowers mature to an ovoid acorn, 1/2 to 3/4 inch long, that has a cup that varies from cup shaped to turbanate (narrowed at the base). The cup covers 1/3 to 1/2 the acorn and has a fringed border of loose (particularly on the cap edges) rust-brown scales. The outer surface of the cup can have very fine hair. Acorns are biennial - taking 2 years to mature as do most species in Quercus Sect. Lobatae, which contains the Red Oak Group.
Habitat: Black Oak grows from a deep taproot and spreading lateral roots. Its preferred sites are dry upland slopes or sandy lowlands. Full sun is required for a good shape. Black Oak will hybridize with Pin Oak, Northern Pin Oak and Northern Red Oak. Oaks should be pruned during the winter months, from October to March, to avoid open wounds where the Oak Wilt fungus can enter.
Names: The genus name, Quercus, is the Latin word for Oak. The species velutina, means 'velvety'. The author name for the plant classification - ‘Lam.’ is for Jean-Baptiste Lamarck (1744-1829) French naturalist who published on botany and zoology and is known for his theory of the inheritance of acquired characteristics.
Comparisons: The Northern Pin Oak, Quercus ellipsoidalis, is a similar Oak in appearance with sharp pointed lobes on the leaves but the lobe cuts are broader. However, the acorn does not have scales on the cup that are as loose as those of Black Oak nor do they have as much fine hair. Twig buds of Black Oak are also larger and more fuzzy. The only oaks with similar characteristics are the Northern Red Oak, Pin Oak and Scarlet Oak.. Check the Oak Leaf Comparison Sheet.
Above: A mature Black Oak tree. Drawing from Britton, N.L., and A. Brown. 1913. An Illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: The acorn cup varies from cup shaped to turbanate. Mature acorns have a cup covering 1/3 to 1/2 the acorn. Scales are loose at the border of the cup. Acorns mature in the second year.
Below: The female flowers are on short spurs on new growth (1st photo). Terminal buds have 5 angles in cross-section (2nd photo).
Below: The male catkins form with the leaves (1st and 2nd photo) from buds at the end of the prior years twig. The only hair on the leaf will be tufts in the underside vein joints.
Below: Leaf shapes vary but are elliptical overall with a long stalk and the base lobes are usually slightly unequal. The underside (3rd photo) is much paler color.
Below: Bark becomes blackish, thick and rough and deeply furrowed into ridges that have horizontal breaks. Newer twigs (2nd photo) are grayish green to reddish-brown in color, with many small lenticels, usually smooth. The buds are large, buff in color, with fuzzy hair, and jut out at angles from the twig. Older twigs (3rd photo) are gray and still show the lenticels.
Below: Fall leaf color has some red tinges to begin, then turning dull red or brown.
Notes: Black Oak first arrived in the Wildflower Garden on Oct. 17, 1913 when Eloise Butler planted some acorns she had obtained from the Arnold Arboretum. In 1917 she planted 13 acorns collected in Providence Rhode Island. The tree was not present by the time of Martha Crone's 1951 plant census. Gardener Cary George replanted the species in 1994 but it was not listed on the 2009 census. In Minnesota the tree is found in the wild only in Goodhue, Houston, Wabasha and Winona Counties - this SE corner of Minnesota is the northwestern extent of its range in North America. It is found in the eastern half of the U.S. and in Ontario in Canada.
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.
Wood and its Uses: The bark of Black Oak is a rich source of tannins for the leather industry. The yellow inner bark also supplied a yellow dye (called Quercitron) that was obtained by drying the peeled bark, pounding it to a powder and sifting out the yellow dye material.
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 invisibilty. 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"