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Winter Key to Native Oaks of Maryland

(Quercus genus) 1/24/12 Cris Fleming

From Brown and Brown, Woody Plants of Maryland (plus other books and personal observation). The descriptions below are visible under 10 power magnification.

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  • 1a. Fruit maturing the first year, no immature acorns on twigs; lobes of any persisting leaves not bristle-tipped; inner surface of acorn shell smooth; base of cup (where attaches to stalk) usually roundish; buds roundish or ovoid ==> White oak group, 2
    • 2a. Bark light gray, flaky to ridged ==> 3
      • 3a. Buds subglobose or ellipsoid, nearly or quite glabrous ==> 4
        • 4a. Buds 3-5 mm. long, reddish brown, with some pale hairs; twigs reddish-purple to gray, glabrous; bark light gray with shallow furrows below and peeling ridges on upper part of tree, lower branches not drooping; acorns ovoid, up to 2cm. long with shallow cup, bumpy scales, and short stalk, roots form early ==> Q. alba (White Oak)
        • 4b. Buds 2-4 mm., roundish, smooth, orangish-brown; twigs tan, tinted with orange, usually glabrous; lower branches usually drooping; bark similar to Q. alba but rougher with deeper furrows, peels in thin curls; acorn over 2 cm. with deep cup over at least ½ of nut, covered in grayish pubescence with thick, pointed scales and lower scales fringed, long thin stalk up to 10cm. ==> Q. bicolor (Swamp White Oak)
      • 3b. Buds ovoid or conical ovoid ==> 5
        • 5a. Twigs moderate, yellow to tan, new growth with yellowish pubescence; buds 2-4 mm., reddish-brown, pubescent to silky; bark light gray, rough, scaly; acorns about 2 cm. with very short stalk, cup with narrow scales covering about ½ of nut, cup often retained on twigs ==> Q. stellata (Post Oak)
        • 5b. Twigs stout, gray, or gray tinted with orange, pubescent to glabrate; (2nd year twigs with corky ridges); buds 3-6 mm. gray pubescent, more conical than others in White Oak group; buds and leaf scars raised; terminal bud; bark thick in long rectangular twisted ridges, pale to medium gray; very large acorns up to 5 cm. with deep bowl-shaped cup covering almost the entire nut, lower scales deeply fringed ==> Q. macrocarpa (Bur Oak)
        • 5c. Twigs orange to orange brown or somewhat grayish ==> 6
          • 6a. Buds to 6 mm, reddish or orangeish, acute at tips, scales puberulous with (darker) margins, twigs reddish-brown to grayish with some short-lived hairs; (bark pale gray, shallowly furrowed with flaky ridges, similar to Q. alba; acorn usually stalked, 2.5-3.5 cm. long, obovoid and stout, light reddish brown, cup thin and bowl-shaped, scales of cup densely puberulent, pointed and free to base) ==> Q. michauxii (Swamp Chestnut Oak)
          • 6b. Buds 3 mm., acute, brown, puberulent or glabrous, scales often pale-margined; twigs orange-brown, slender; bark pale gray, flaky, very similar to Q. alba; nuts ovoid, 1.2-2 cm. long, short-stalked, cup less than ½ length of nut, with grayish-brown tomentose scales free only at tips) ==> Q. muehlenbergii (Chinkapin Oak)
          • 6c. Buds 3 mm, obtuse (blunt), light brown, with pale tomentum near margins of scales; twigs slender, young twigs pubescent, greenish-red, older twigs usually glabrous orange to grayish brown; bark light gray with scaly ridges; acorn almost globose 1.2-2.5 cm. long, nearly covered by bowl-shaped cup of bumpy, ragged-edged, pubescent scales ==> Q. lyrata (Overcup Oak)
    • 2b. Bark dark, more or less ridged, usually not flaking==> 7
      • 7a. Tree; buds 5-10 mm, distinctly conical (with pointed tips), reddish-brown, outer scales may have some pale hairs on margin; twigs orange-brown, sometimes tinted with purple, (twigs distinctly angled or ridged; bark very dark gray, with deep V-shaped vertical furrows and broad ridges, inner bark bright reddish-brown); acorn 2.5-3.5 cm. long (large, ovoid nut lustrous brown, with deep bowl-like pubescent cup with thick diamond- shaped scales covering ¼ to ½ of nut) ==> Q. prinus; Q. montana (Chestnut Oak)
      • 7b. Shrub 1-3 m.; buds 1.5-3 mm. (buds ovoid; twigs glabrous; bark gray with scaly ridges; acorns 1-1.5 cm.long, short-stalked blunt cup with hairy scales covers 1/3-1/2 of nut) ==> Q. prinoides (Dwarf Chestnut Oak)
  • 1b. Fruit maturing at end of second season, immature acorns on twigs; lobes of any persistent leaves bristle-tipped; shells of mature acorns hairy on the inner surface, scales of cup thin; buds more or less pointed, base of acorn cups (where attached to stalk) in some species is thick, knobby, and/or top-shaped; Red Oak group ==> 8
    • 8a. Trees ==> 9
      • 9a. Buds definitely angular in cross section ==> 10
        • 10a. Buds 6-12 mm. long, very hairy or tomentose ==> 11
          • 11a. Buds ovoid (and pointed); scales tan with soft pubescense; (twigs glabrous, strongly angled; bark dark brown-gray with irregular rectangular blocks; inner bark yellow; acorn with thick, short stalk, broadly ovoid to round, pubescent; deep bowl-shaped clasping cup covers at least ½ of nut, long pale scales forming a broad fringe) ==> Q. velutina (Black Oak)
          • 11b. Buds long-ovoid to conical with woolly rusty-brown pubescence (somewhat angled; twigs stout, pubescent; bark thick, rough, nearly black with deep fissures and scaly blocks, inner bark orange; tree usually under 20 meters, grows in poor soil; acorn ovoid, short- stalked, deep cup top-shaped with loose pubescent scales) ==> Q. marilandica (Blackjack Oak)
        • 10b. Buds to 6 mm. long, glabrous; twigs glabrous or thinly pubescent ==> 12
          • 12a. Buds long- ovoid, 4-6 mm. long, light brown (sharply pointed, edges of scales thin and papery); twigs pale brown (or grayish-brown; large tree with deeply furrowed bark, furrows dark brown and ridges much lighter, flat and scaly; acorn 1.5-3 cm. long, thick light brown cup saucer-shaped with puberulent scales, edges of lower scales fringed and clasping nut) ==>Q. shumardii (Shumard’s Oak)
          • 12b. Buds ovoid, 3-6 mm. long, dark reddish-brown (acute, angled); young twigs dull red (older twigs grayish, bark medium gray with irregular ridges, acorns 1-1.5 cm. long, cup shallow saucer with tight scales. In MD, found on eastern shore along streams or in wet woods) ==> Q. nigra (Water Oak)
      • 9b. Buds not angular in cross-section, or only slightly so ==> 13
        • 13a. Buds usually not over 3 mm. long, ovoid, acute ==> 14
          • 14a. Buds reddish to reddish-brown, scale margins with pale hairs; slender, glabrous twigs reddish or greenish (brown, mature bark very dark with narrow ridges; acorn very small, 1 cm. or less, globose, cup shallow, saucer-like, scales tight and pubescent) ==> Q. phellos (Willow oak)
          • 14b. Buds brown with some gray pubescence (buds ovoid, sharp-pointed); twigs brown, glabrous; (bark dark brown in low ridges; acorns ovoid to globose, 12-18 mm. long, about 1/3-1/2 covered by thin cup with blunt pubescent scales) ==> Q. imbricaria (Shingle Oak)
        • 13b. Buds ovoid, usually 3 mm. or larger ==> 15
          • 15a. Twigs glabrous (or soon so) ==> 16
            • 16a. Tip of bud pubescent or slightly hairy ==> 17
              • 17a. Buds 5-8 mm. long, red or reddish-brown (upper scales often ciliate); twigs dark red to reddish brown or olive tinted with red; (bark gray with darker vertical deep fissures like xc ski tracks; acorn 2-3 cm. long, stout, broadly ovoid with shallow tightly-scaled beret-like cup) ==> Q. rubra (Red Oak)
              • 17b. Buds 3-6 mm. long, brown (with silvery-whitish pubescence on upper scales); twigs slender, brown or reddish brown; (bark gray, rough with irregular vertical shallow fissures, inner bark reddish; acorn 12-20 mm. long, usually with a series of circles at the base of nut; deep top-shaped cup of tight glossy triangular scales covering at least half of the nut) ==> Q. coccinea (Scarlet Oak)
            • 16b. Bud scales glabrous (but ciliate on the margins), buds 3-4 mm. long, brown; (twigs slender, olive-brown to brown or gray, lower branches and twigs drooping down; bark gray with irregular darker shallow fissures; acorns small, 1-1/5 cm. long, globose, light brown, often with lighter striations and a light flat circle on top, shallow beret-like cup of tightly appressed scales, short stalked) ==> Q. palustris (Pin Oak)
          • 15b. Young twigs pubescent, reddish-brown to brown, (sometimes tinted with olive); buds 3-7 mm. long, red to reddish-brown, with pale hairs, (ovoid- acute; bark dark gray with shallow long fissures; acorns 1-1.5 cm, subglobose, about ¼ to ¾ covered with a shallow cup with blunt, pubescent scales) ==> Q. falcata (Southern Red Oak)
    • 8b. Shrub; much branched, giving the appearance of many stems; buds 3-4 mm. long, with broad, ovoid, rounded apex, brown; twigs brown to reddish-gray, pubescent the first winter; (bark dark brown and scaly on trunk, smoother on twigs, acorns usually in pairs, about 1 cm. long, glossy, ¼-½ covered with roundish cups of tight scales) ==> Q. ilicifolia (Bear Oak)

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