Mystery Plant! #750

John Nelson

Posted 11/22/23

By John Nelson
johnbnelson@sc.rr.com

(Photo by John Nelson.)
An oak tree is just an acorn’s way of making more acorns.
                                                            –an old saying

All of the 400 or so species of oaks in the world belong to the genus Quercus, and North Americans are blessed with about 100 of them. You may have heard that American oaks, that is, those in the Southeast, can be split, roughly, into three groups: the “red” oaks and the “white” oaks, as well as the “live” oaks. Red oaks typically have leaves with sharp-pointed lobes, and with bristles on the tips. Red oaks’ acorns take two years to mature before falling. White oaks’ leaves have lobes with rounded tips, and their acorns mature in one year. Live oaks and their close relatives generally don’t have lobed leaves. There are a good many additional technical differences separating these, but let’s not bother here.

(Photo by John Nelson.)

The other day I was able to tag along on a field trip with the SC Native Plant Society, deep into the far corners of the Congaree National Park, not too far from my hometown. Our trip leader was John Cely, who was one of the lead instigators in the protection of the “Congaree Swamp” as a natural area way back in the early 1970s (and now, CNP is the only National Park in South Carolina). Besides being an expert ornithologist, John is probably the most knowledgeable person concerning the natural habitats within the Congaree National Park. If there was ever anybody with whom I would want to be down there on a cloudy day without a compass, it is John Cely; he knows the area like the back of his hand.

Our merry band was led around to see some of the tallest trees of the swamp, and we were not displeased with what we saw. This oak is one of the highlights.

It’s a plant of lowlands, particularly swampy or otherwise occasionally flooded places, and is thus often seen within river floodplains, from Maryland to Texas, and into the Mississippi Valley. This particular individual is 17 feet in circumference, meaning that is has a diameter of nearly six feet, and is nearly 100 feet tall. It’s growing in a very flat landscape, a sort of lower terrace within the floodplain, and of course that means that the soil is exceptionally rich, which in large part accounts for the size of some of these giants. Its bark is pale, and reminds us of the familiar white oak, Quercus alba. Its leaves tend to be similar, too, to white oak, although the blade has a bit of narrowing about halfway toward the tip, and some botanical classicists have likened the leaf shape to that of an ancient lyre, or fiddle-shaped.

But it’s the acorns of this species which really set it apart from the other oaks. The acorns are fairly large, up to nearly 1.5 inches, a lot like a similar species, Quercus michauxii, the “swamp chestnut oak”, which grows in similar swampy habitats. Our mysterious oak, though, has it acorns almost covered totally by a scaly cap, with the only the very tip of the nut showing through.

[Answer: “Overcup oak,” Quercus lyrata]

John Nelson is the retired curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or email johnbnelson@sc.rr.com.

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