Tom's Blog

Friday, October 21, 2011

More on Hill's oak

In a recent post I mentioned that Hill's oak (Quercus ellipsoidalis) is easy to identify this time of year because of its distinctive fall color. I should be doing an intensive survey for this species now, but unfortunately can't find the time. However, even from casual observations I am finding new specimens that we had previously classified as black oaks. Yesterday I noticed that there were several small trees with typical Hill's oak color at the top of the ravine west of the woods road. Then, as I drove down the woods road I kept on the lookout for further trees. Sure enough. Almost at the bottom of the hill, right next to the Pocket Prairie, was a tree with the distinctive Hill's color. This tree was large enough that it was in our database, classified incorrectly as a black oak. I pushed my way through the tall Indian grass of the Pocket Prairie to this tree and discovered that it was tree # 1513.

Not only was the color distinctive, but the shape was also characteristic of Hill's, including the lower dead branches. Finally, on the ground under the tree were quite a few acorns with the characteristic Hill's structure (ellipsoidal and striped).

The accepted common name for this species now seems to be northern pin oak, but I find Hill's more felicitous and lots easier to say.

There is another pin oak (Quercus palustris) which is not found in Wisconsin or the upper Midwest but lives in a wide band across the middle of the United States.

According to what I have been told by foresters, the word "pin" as part of the common names of these two oaks, comes from the fact that the lower dead branches, sticking straight out, can be thought of as "pins."

The tree in this photo is not too far from the outlet from the ravine, and since there is a large patch of Hill's oaks at the top of the ravine, it seems reasonable that acorns might find there way down to the bottom. I used GIS to determine that tree #1513 is about 800 feet from the Hill's oak grove at the top of the hill.

I picked up this little "gimmick", attributed to the Morton Arboretum, from someone's Facebook page:
Know, know, know your oaks,
this is how they grow:
Red oak (make a V with your arms above your head)
White oak (hold your arms straight out from your shoulders)
Bur oak (make your arms twist in different directions)
Pin Oak (hold your arms down at your sides)
And Hill's untidy below.


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