The White Oak Group

This fall, one of my quests is to collect leaves from all eight oak species that can be found in Maine forests. There are four in the black oak group: Northern Red Oak (Quercus rubra), Black Oak (Q. velutina), Scarlet Oak (Q. coccinea), and Bear Oak (Q. ilicifolia). Four more are grouped as white oak: White Oak (Q. alba), Chestnut Oak (Q. prinus), Bur Oak (Q. macrocarpa) and Swamp White Oak (Q. bicolor). Black oak leaves have bristly lobe tips, and the acorns take two years to mature while white oaks have rounded lobes or teeth with acorns maturing every year.

Thus far the teaching collection includes specimens from Northern Red Oak, Scarlet Oak, White Oak, and Swamp White Oak - halfway there!

The question today is what species of oak is represented by the leaves and bark pictured. Situated in a planted community, the tree is labeled White Oak (Q. alba). However, the Forest Trees of Maine describe White Oak leaves as dull above with rounded lobes, and the bark as having broad, flat, flaky ridges - neither of which seems to match up to this tree. Years ago I might have walked away thinking, "Okay, this is an atypical White Oak" but nowadays I question everything (especially myself). My goal isn't to discount someone else's work but rather to firm up my own understanding. So I'll bring you along on today's quest and questions - perhaps you'll weigh in with thoughts or answers.

First, what do I see? For me, direct observations in the field and photographs for later reference are the first step in identification. Instead of taking a field guide or key and trying to fit a specimen into that format, I attempt to learn by looking first at the features in front of me. Here's what I noted:

• Acorns: still forming, will continue to watch them develop. All eight oaks develop acorns: the black oak group takes two years to mature while the white oak group's acorns mature every year. This tree's acorns are still forming so I'll check back frequently over the next month or so for developments.
• Buds: still forming, will continue to watch. Winter buds begin developing at the leaf base during the summer. Breaking off the leaf doesn't reveal anything definitive yet so this is another feature I'll track over the next few weeks.
• Leaves: alternate, simple, lacking lobes, rounded "teeth" without bristly tips, deep glossy green above, wedge-shaped base. The rounded edges definitely put this leaf into the white oak group - no bristly tips. Not distinctly lobed like White Oak or Bur Oak, this can be narrowed down to either Chestnut Oak or Swamp White Oak - if we believe it to be a Maine tree. A planted grove may include other species so there's a possibility that it's a non-Maine native or a hybrid.
• Bark: deep fissures with orange at fissure base, irregular chunky ridges, gray-brown. 

Now let's compare observations and photo documentation with keys and field guides.

White Oak Quercus alba	Short-stalked (F) Cup bowl-shaped covering 1/3 or less of acorn (P)	2-4 times longer than acorn cup, hairless (F) End-buds red-brown, small, blunt, hairless (P)	Hairless (P)	Dull upper, rounded lobes (F) Evenly lobed, hairless, somewhat white below (P)	Broad flat ridges, flaky (F) Whitish, furrows broken into rectangular blocks (B) Whitish, slightly furrowed to scaly (P)
Chestnut Oak Q. prinus	3 times as long as cup, long & wrinkled (F) Cup bowl-shaped, tight scales free only at tip, < 1” across (P)	Sharp-pointed, broadly ovoid, hairless (F) End-buds narrow, sharp, > 3/16” (P)	Hairless (P)	Shiny upper, shallow rounded lobes (F) 7-16 pair of rounded teeth, leathery, slightly hairy below (P)	Deeply furrowed (F) Firm flat-topped ridges broken horizontally into irregular blocks with crisp square edges – corrugated & angular (B) Dark, deeply ridged (P)
Bur Oak Q. macrocarpa	2 times as long as cup, margin fringed with long hair-like scales, short-stalked (F) Bowl-shaped with fringe of elongate scales (P)	Broad ovoid, blunt or sharp-pointed, coated with soft hairs (F) End-buds blunt and hairy, > 3/16” (P)	Yellow-brown, hairless to hairy; branchlets may have corky wings (P)	Dark green & shiny upper, violin shaped (F) At least one pair indentations divide leaves into 2 or more portions, somewhat hairy & whitish below (P)	Deeply furrowed, flaky (F) Deeply furrowed, rough scaly ridges are not flaky, thick irregular blocks (B) Light gray, shallowly grooved (P)
Swamp White Oak Q. bicolor	3 times as long as cup, margins fringed with scales, long-stalked (F) Bowl-shaped cup with stalks longer than leaf-stalks (P)	Roundish, blunt-pointed, hairless (F) Brown end-buds small, blunt, hairless (P)	Hairless (P)	Dark green dull upper, slightly lobed (F) 4-6 pair of large rounded teeth, sometimes shallow lobes, wedge-shaped base, white-hairy beneath (P)	Deeply fissured, broad flat ridges, flaky, inner bark orange (F) Irregular furrows, narrow scaly ridges broken into horizontal blocks (B) Light gray, ridged or flaky (P)

F  = Maine Forest Service. 1908 (rev 2008). ForestTrees of Maine. Maine Department of Conservation.

B = Wojtech, Michael. 2011. Bark: A Field Guide to Trees of the Northeast. Hanover: University Press of New England.

P = Petrides, George A. 1958 (1972 2^nd ed). A Field Guide to Trees and Shrubs. Boston: Houghton Mifflin Company.

Buds and acorns on the planted species will yield information toward making a definitive identification. The shiny upper leaf with 8-9 pair of lobes suggests Chestnut Oak. Now off to southern Maine in search of field species to compare with those planted.



UPDATE: Here are leaves seen on a sapling at Mt. Agamenticus where the Maine Natural Areas Program's Natural Landscapes of Maine has documented Chestnut Oak as a natural community. Though the Mt. Agamenticus Wildlife Management Area does not allow specimen collection, I was able to get this photo to use as comparison with the planted specimen above - what do you think?