Oak Key

The Oaks
Quercus sp.

The Oaks form a large genus, of which 52 species are North American. Of these, 12 are native to the New England region. Buds clustered at ends of twigs, more or less 5-sided pyramidal, covered with 5 rows of closely overlapping brownish scales. Leaf-scars concave to rounded above, rounded at base, generally broader than high and raised with a ridge more or less well-marked, decurrent from lower edge, the ridges from the 5 ranks of leaf-scars causing twig to be more or less 5-angled especially when dried. Bundle-scars irregularly scattered, inconspicuous. Stipule-scars inconspicuous. Pith of cut twig 5-pointed, star-shaped. Cross-section of branch or trunk showing layers of large, porous spring wood alternating with dense layers of summer wood. Medullary rays of wood very prominent, apparent as radial lines in cross-sections of a log, also generally showing prominently (especially through a hand-lens) on cut ends of stout branchlets of several years growth. Fruit an acorn enclosed in a scaly cup. Dead leaves often persistent on the tree during winter. Different species occupy many ecological conditions in the region.

109.	Fruit maturing in autumn of second year, ripe acorns therefore borne upon parts of twig two years old; immature acorns to be found in winter on twigs of the past season's growth; shell of nut hairy inside; abortive ovules at the top of the nut; scales of acorn-cup broad and thin; lobes of leaves bristle-pointed.	See Black Oaks 110
109.	Fruit maturing in one year, ripe acorns therefore borne upon last season's growth; no immature acorns to be found upon twigs in winter; shell of nut smooth inside; abortive ovules at base of nut; lower scales at least of acorn cup more or less thickened at base giving a knobby appearance to surface of cup; scales more or less densely woolly; kernel commonly sweetish; lobes of leaves not bristle-pointed; bark flaky except in Chestnut Oak.	See White Oaks 114
110.	Cup of acorn shallow, saucer-shaped.	111
110.	Cup shaped like a top.	112
111.	Cup thin, 15 mm. or less wide; buds 4 mm. or less long.	Quercus palustris, Pin Oak
111.	Cup thick, 20 mm. or more wide; buds over 4 mm. or less long.	Quercus rubra, Red Oak
112.	Buds over 4 mm. long; twigs slender; shrubs.	Quercus ilicifolia, Bear Oak
112.	Buds over 4.5 mm. long; twigs rather stout; trees.	113
113.	Upper scales of cup loosely overlapping; buds pointed, whole surface woolly; inner bark yellow.	Quercus velutina, Black Oak
113.	Upper scales of cup closely overlapping; buds blunt, downy above middle; inner bark pale red.	Quercus coccinea, Scarlet Oak
114.	Upper scales of cup with thread-like outgrowths forming a fringe to cup; branchlets often with corky ridges; lateral buds frequently appressed.	Quercus macrocarpa, Bur Oak
114.	Cup without distinct fringe; branchlets without corky ridges; lateral buds divergent.	115
115.	Bark on branchlets peeling back in dark stiff-papery layers; marginal scales of cup narrow awn-pointed; acorns long-stalked.	Quercus bicolor, Swamp White Oak
115.	Bark on branchlets not peeling back in dark stiff-papery layers; acorns sessile (without a stalk) or short-stalked (at times long-stalked in White Oak).	116
116.	Buds sharp-pointed.	117
116.	Buds blunt.	118
117.	Nut 20 to 35 mm. long; buds 4 to 10 mm. long; bark thick, furrowed, not flaky.	Quercus prinus, Chestnut Oak
117.	Nut 15 to 20 mm. long; buds 3 to 6 mm. long; bark thin, flaky.	Quercus muhlenbergii, Chinquapin Oak
118.	Twigs slender, generally not over 2 mm. thick; shrubs.	Quercus prinoides, Dwarf Chinquapin Oak
118.	Twigs relatively stout, generally over 2 mm. thick; trees.	119
119.	Twigs, at least in part, covered with very fine close olive-green down; buds generally nearly hemispherical, about as broad as long; scales of cup only slightly knobby; apex of nut generally downy.	Quercus stellata, Post Oak
119.	Twigs smooth; buds distinctly longer than broad, broadly ovate; scales of cup thick-knobby at base; apex of nut generally smooth.	Quercus alba, White Oak

120.	Buds large, those at tip of twig 4.5 mm. or more long.	121
120.	Buds smaller, less than 4.5 mm. long.	128
121.	Bark of trunk flaky.	122
121.	Bark of trunk not flaky.	124
122.	Lateral buds generally appressed, buds downy; older twigs often with corky ridges.	Quercus macrocarpa, Bur Oak (W)
122.	Lateral buds divergent, buds smooth; twigs without corky ridges.	123
123.	Buds narrow conical, pointed.	Quercus muhlenbergii, Chinquapin Oak (W)
123.	Buds shorter, blunt.	Quercus alba, White Oak (W)
124.	Surface of buds woolly.	125
124.	Surface of buds not woolly.	127
125.	Inner bark of trunk orange-yellow; whole surface of bud woolly; buds large, ovate-conical.	Quercus velutina, Black Oak (B)
125.	Inner bark of trunk not yellow; not more than upper half of bud woolly.	126
126.	Buds sharp-pointed; ovate, the widest part being 25% to 67% of the way above the base; slightly or not at all woolly toward apex.	Quercus rubra, Red Oak (B)
126.	Buds blunt-pointed; oval-ovate, the widest part at (or slightly below) middle; distinctly woolly above middle.	Quercus coccinea, Scarlet Oak (B)
127.	Fissures of bark separated by long flat ridges; buds ovate, more or less constricted at base; twigs not bitter.	Quercus rubra, Red Oak (B)
127.	Fissures of bark separated by long rounded ridges; buds narrower, conical, seldom constricted at base; twigs more or less bitter when chewed.	Quercus prinus, Chestnut Oak (W)
128.	Buds narrow, conical.	129
128.	Buds short, blunt.	132
129.	Bark of trunk flaky.	130
129.	Bark of trunk not flaky.	131
130.	Buds downy, lateral buds generally appressed; older twigs often with corky ridges.	Quercus macrocarpa, Bur Oak (W)
130.	Buds smooth, lateral buds divergent; twigs without corky ridges.	Quercus muhlenbergii, Chinquapin Oak (W)
131.	Twigs of past season dull, finely downy; shrubby form.	Quercus ilicifolia, Bear Oak (B)
131.	Twigs smooth, shining; slender pin-like twigs numerous, arising at nearly a right angle with the branchlets; a tree.	Quercus palustris, Pin Oak (B)
132.	Bark on branchlets peeling into long, dark, stiff-papery layers.	Quercus bicolor, Swamp White Oak (W)
132.	Bark on branchlets not peeling into long, dark, stiff-papery layers.	133
133.	Twigs slender, generally not over 2 mm. thick; shrubs.	134
133.	Twigs stout, generally over 2 mm. thick; trees.	135
134.	Bark of trunk smooth; young acorns generally found on winter twigs; buds more generally conical.	Quercus ilicifolia, Bear Oak (B)
134.	Bark of trunk flaky; young acorns never found on winter twigs.	Quercus prinoides, Dwarf Chinquapin Oak (W)
135.	Lateral buds generally appressed; buds densely downy; older twigs often with corky ridges .	Quercus macrocarpa, Bur Oak (W)
135.	Lateral buds divergent; buds not densely downy; twigs without corky ridges.	136
136.	Twigs at least in part covered with very fine close orange-brown down; buds generally nearly hemispherical and about as broad as long.	Quercus stellata, Post Oak (W)
136.	Twigs smooth; buds broadly ovate, distinctly longer than broad.	Quercus alba, White Oak (W)