What kind of red oak?

[sradivoy]

Hi folks,
I need help identifying this species of red oak? It has very shallow bristle tipped lobes. I'm thinking a variety of Nothern red. The bark looks like a black oak but the leaves are matte green like a Q. rubra. Perhaps a hybrid between the two? Both species are nearby, including many pin oak, but are located in a city park and most likely planted. I don't have acorns. Thx!

[Erik Danielsen]

It would help to see what the bark looks like moving further up the trunk. The bark shown is reminiscent of velutina but rubra can also look like that near the base, varying greatly between individuals. The leaf looks like a relatively fresh one from low on the tree, where leaf-forms are often "filled-in" looking to catch more light relative to more typical leaves higher up in the crown and especially likely to be funky if they're on an epicormic shoot. Leaf texture does look more rubra-like from the photo but fresher leaves can be deceptive ("velutina" actually refers to the velvety texture of that species' very early leaves).

Of course, some degree of hybrid traits is very possible, but traits between the two species can overlap so much even without.

[AndrewJoslin]

Those are strong Black Oak bark characteristics.

[sradivoy]

Went back to take some more photos of the tree in question just a couple of blocks away from where I live. I think its a young Eastern black oak. The bark is pretty much the same all the way up and the leaves on top where more deeply lobed and they had the wet sheen characteristic of the black oak when the sun reflects on it. But I've never seen leaves like that on a black oak before. According to the leaf diagrams of the book I was carrying with me ("Woody Plants of Ohio" by Lucy Braun) the leaves most closely resemble the Blackjack oak (Q. marilandica) or the hybrid Q. bushii (Q. marilandica x velutina), neither of which I'm familiar with.

[Erik Danielsen]

Thanks, that texture extending up the trunk certainly eliminates rubra. I spend some time in stands with velutina, marilandica, and x bushii here- leaf-wise this is standard velutina. Leaves on low branches (especially sprouts from the trunk) on many oaks develop with "modifications" for absorbing more light, such as increased surface area.

[sradivoy]

Thanks Eric. Interesting. Do these modifications occur with the pin oak as well. Also, what are some of the bark, leaf, and acorn characteristics differentiating the rubra var maxima and the rubra var borealis. Any pictures would be great. And thanks for your expertise!

[pattyjenkins1]

For those not familiar with it, the University of Georgia has a website called ForestryImages.org which has a searchable database of thousands of pictures of all the different features of individual trees. I used it extensively for the "Common Trees of Atlanta" section of my new TreeInspection.com website.

patty

[Erik Danielsen]

I don't know if I'd quite stretch my observations of certain oaks to the point of expertise! It's really just more that one year ago I moved from a region with nothing but northern red oak to a region with over a dozen oak species (and hybrids!), so I've had to put myself through a crash course on the different species present here and spend a lot of time obsessively looking at the details. I still get confused by some but think I've got a much better handle on it, but much moreso for certain species than others.

I haven't observed as much of that sort of leaf modification in pin oak, but I wouldn't be surprised if it can happen there. Really the situations where I see odd leaf forms in various oaks are in reaction to stress (new shoots resprouting after the main stem gets knocked off or burned to the ground, or on trees with obviously diseased trunks), on saplings trying to maximize photosynthesis in the understory, and on shaded lower branches, particularly adventitious sprouts from lower on the main trunk.

Regarding rubra variations I really have no idea. According to the ITIS standards page it doesn't appear that those variations are still recognized? USDA profile does list rubra var. rubra and rubra var. ambigua. From the degree of variation I see in any given stretch of woods I think Quercus ambigua ought to be the actual species name! From an older source regarding borealis/maxima:

Northern Red Oak (Q. rubra)
Several traits related to geographic origin were identified for northern
red oak in a 14-year provenance test in

the North- Central States. Time of flushing is earliest for trees of
northwestern origin. The trend is then

eastward and southward. Autumn leaf coloration is earliest for
provenances from northern latitudes and then

progresses southward. Provenances from regions at the western edge of
the northern red oak range, where

periods of high summer temperatures and drought are common, survived
better under such conditions than

other provenances. Much variation in height growth was present and
performance of the provenances was not

consistent in all tests. The only consistent difference was the slower
growth of the northern provenances in

areas farther south. The within-family variation was so great it
obscured any real differences in geographic

origin (15).

Races
The nomenclature for northern red oak was confused for some time. The
scientific names Quercus borealis

Michx. f. and Q. borealis var. maxima (Marsh.) Sarg. were adopted after
1915 by some authors, but in 1950,

Quercus rubra L., the name in universal use before 1915, was restored
(17).


Steve Galehouse related this in 2007:

"An additional comment regarding the red oaks is the nomenclature of
/Quercus rubra/, Northern Red Oak. Old texts list it as /Quercus
borealis/, with two primary "varieties", /Q. borealis borealis/, and /Q.
borealis maxima./

These two varieties look very distinct to me, with /Q. borealis
borealis/ having much smaller acorns with a deeper cup, much more
deeply fissured bark, a more northerly range, and a smaller, scrubbier
habit when compared to /Q. borealis maxima/(which is the commoner type,
and I believe what most people think of as /Q. rubra.

/For me at least, these two types are as or more distinct than /Q.
velutina/ compared to /Q. coccinea."

The borealis/maxima variations did come up in a facebook conversation recently that a few BBS members participated in, so it may be that someone more experienced here will have further insight into the subject.

[sradivoy]

Interesting how the pointed lobes of the velutina leaf become rounded with its epicormic shoots as the sinuses become very shallow. I've seen plenty of low lying leaves of rubra and palustris that have shallow sinuses while maintaining pointed lobes. Could this be used as a diagnostic characteristic for the velutina or are there others that you know of? Also, are the epicormic shoots commonly seen on the pin oak a function of the small surface area of its leaves on top? It seems more normal on this species than others and not an indication of poor health. I see a lot of it in unhealthy ash trees with dead tops.

[Erik Danielsen]

I think you're right, that degree of rounding does seem more typical at least in my limited observing of velutina than, say, rubra which "fills in" but remains more pointed. I'd be interested to see where coccinea falls on this spectrum since it's considered to be very close to velutina.

Regarding pin oak, that's an interesting line of questioning. I would speculate this- epicormic shoots are usually a reaction to some kind of stress, including damage to or restriction of oxygen or nutrients to the roots. Pin Oak is by default adapted to palustrine environments where many other species would find oxygen to their roots more restricted than they'd prefer. Perhaps epicormic shoots being just the "normal" for pin oak just reflects their adaptation to a niche many other trees would find stressful. I suppose that's wildly speculative however!