Friday, December 10, 2010
The last time I wrote about an oak tree (November 5, 2010) was a result of the Trails Committee walk at Foss Farm. The species was the Swamp White Oak. Today I have another oak from another Trails Committee walk. This time it is the Chestnut Oak and it turned up on the day-after-Thanksgiving walk at Great Brook Farm State Park. Judging by the number of Chestnut Oak leaves on the ground among all the other dead leaves, there must be several Chestnut Oaks near the highest point on Stone Row trail. All the trees up there were bare of leaves and I wasn’t able to recognize the tree by its bark. If I had known more at the time, I would have looked for trees with very thick and deeply ridged bark.
Name: The Chestnut Oak, like the Swamp White Oak, is a member of the
“white” oak group of oaks. Its common name is due to the shape of its leaves which are more like those of a Chestnut than most of the other oaks. It also has several other common names. One of those, Rock Oak, is because it is typically found in poor dry soil on rocky ridges (like Stone Row) as it can’t compete with other hardwoods on better soil. Another name is Tanbark Oak because the bark is the best source of white oak tannin with around 11 per cent tannin and was once used to tan leather. Hemlock bark was also used for tanning but imparted a red color which could be minimized by mixing in Chestnut Oak. The Latin name for the tree, Quercus prinus, was given by Linnaeus but has apparently been applied to other species and the taxonomists are now suggesting we clear the air in a big-sky way and call it Quercus montana.
Distinguishing characteristics: The leaves are much longer than they are wide. The lobes are very shallow and look more like rounded blunt teeth than lobes. Other oaks with similar leaves are the Chinkapin and the Swamp Chestnut Oak, both of which are found only south and west of here. For us, a combination of the leaf shape and the habitat should be enough for an ID. The true Chestnut leaf is the same general shape but has more teeth and they end in a bristle or spine.
Red Oak vs. White Oak: The most easily observable difference between white oaks and red oaks is that red oaks have bristles at the tip of the leaf lobes. Another difference is that acorns of white oaks are sweeter than those of red oaks and contain much less tannin – so if you are compelled to try eating them (as some of us are) you’d be wise to choose something in the white oak family. More on that in a minute. Another interesting difference in these families is that the vessels in the heartwood of white oaks are clogged. This means it won’t absorb liquid which makes it the wood of choice for the wine and liquor industry and also explains why southern Live Oak (another white oak family member) was favored for ship building. The heartwood of red oaks has open vessels and readily absorbs liquid. It is favored in applications where you want penetration of wood preservatives but shunned in the cooperage industry. Like the red oaks, I too have some open vessels and can make wine disappear. There is an increasing amount of evidence that I should have been working on preservatives. Oh well.
Eating acorns: Steve Tobin started this. He made candied acorns from Swamp White Oak and served them (with other goodies) at the end of the Foss Farm Trails Committee walk. He also brought me a bag of raw acorns to try something. After boiling them in approximately ten changes of water to leach out the tannin, I toasted them and ground them into meal. I then took a muffin recipe and replaced half the oat bran with acorn meal and made a quite delicious breakfast. Encouraged by this, next year I will return to the idea of acorn ice cream. The Field Guide to Native Oak Species of Eastern North America reports that acorns from the Swamp Chestnut Oak are “sweet enough to eat raw without boiling”.
References: Audubon Field Guide to North American Trees – Eastern Region, Elbert L. Little; Field Guide to Native Oak Species of Eastern North America, J. Stein, D. Binion and R. Acclavatti; Trees of Eastern and Central United States and Canada, William M. Harlow
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