macrocarpa or alba? or both.....

chizmin

Active Member
Hello all,

I could use some help/opinions. I am attempting to ID a possible state champion Quercus and as you may guess where it lands on the list is going to depend greatly on whether I am looking at a Quercus alba or Quercus macrocarpa.

It is situated near a perennial tributary on what I would describe as a lowland forest in SE WI. Its surrounded by large Populous deltoides, some Tilia, a few Quercus rubra/ellipsoidalis Acer saccharum and other random species. Its relatively wet especially after rain, however the oak i am trying to identify is on a bit higher/dryer portion of land.

It's been shaded out by competing understory so bottom half is all dead branches. From what I can see and find on the ground (i haven't climbed it yet) the majority of the leaves look like Quercus alba, but there are interspersed leaves that look like macrocarpa. From what I can see there is little if any fruit production. I scoured the ground and was able to find some acorns that I am fairly sure came from the oak i'm trying to ID, although I cant be sure. The acorns appear to be stunted or something and many of them are waterlogged/decaying.

The bark is ashy gray and blocky in parts. It is not deeply furrowed in my opinion, especially for a tree this size. There is a bur oak a few miles down that has extremely deep uninterrupted furrows.

At this point I am leaning towards saying it is a Quercus macrocarpa x bur natural hybrid. I've heard them referred to as Bebb Oaks in the past.

What do you guys/gals think?
 

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chizmin

Active Member
Buds and bud scars will be more definitive for identification

Ahh yes I forgot to mention the buds. I have never noticed a defining feature on the buds to separate the two species definitively. The buds were small, although variable. Terminal buds clustered at ends of twigs. Pale red in color, globose, mostly glabrous, possibly some faint pubescence on some. Lack of any stipule structures. I attached a picture below of a lateral bud and scar, although it is terrible, couldn't get them to focus on phone.

Any specific features you are referring to?

Thanks
 

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ATH

Well-Known Member
Q. macrocarpa buds are very distinct with little.....well, burs on the terminal buds. Epidemic twigs are not good for ID as they can be variable. Is that where the leaves are from?
 

chizmin

Active Member
Q. macrocarpa buds are very distinct with little.....well, burs on the terminal buds. Epidemic twigs are not good for ID as they can be variable. Is that where the leaves are from?
The leaves are from broken twigs in the upper canopy from the last storm it appears. There are no epicormic branches in the lower canopy. There are some branches in the upper canopy that are from secondary bud release/adaptive reiteration etc.

Not sure where this particular twig came from.
 
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chizmin

Active Member
Here are some pictures from a colleague of a Q. alba and Q. macrocarpa bud. The main differences I see are usually more bud scales on Q. alba, usually a bit smaller on Q. alba, Q. macrocarpa sometimes a bit more conical, twig is stouter on Q. macrocarpa.

@ATH I don't see the burs you are talking about? Are you referring to the stipule like threads that are on the buds sometimes? I've seen those on Q. macrocarpa and Q. bicolor. I did not find any on the twigs of this oak.
 

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chizmin

Active Member
macrocarpa well have corky twigs and the acorn cap is fringed
Not all bur oak have corky twigs! Also according to Dirr not all have fringed acorn caps either. But both of those are a moot point as the oak is not producing fruit and the fruit I am finding seem dwarfed and I can’t say 100 percent they are from the oak I am trying to ID
 
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ATH

Well-Known Member
the Twigs are not always as corkey as we would like them to be.... But yes the acorns are pretty distinctive. We'll look at this again From the home computer later tonight.
 

ATH

Well-Known Member
Here are some pictures from a colleague of a Q. alba and Q. macrocarpa bud. The main differences I see are usually more bud scales on Q. alba, usually a bit smaller on Q. alba, Q. macrocarpa sometimes a bit more conical, twig is stouter on Q. macrocarpa.

@ATH I don't see the burs you are talking about? Are you referring to the stipule like threads that are on the buds sometimes? I've seen those on Q. macrocarpa and Q. bicolor. I did not find any on the twigs of this oak.
Yes...the stipules. I don't know that I've ever seen a Bur oak without.

I think those acorns were probably aborted, so they aren't very helpful. Hybrid is certainly a strong possibility. that second leaf looks like it could have some Q. bicolor shape in it... maybe a bicolor/alba hybrid? Would hybrids struggle to produce successful seeds???
 

robinia

Well-Known Member
Q x bebbiana is alba x macrocarpa.
It's pretty common and intermediate characteristics.
I don't think sterility is an issue at all. In fact there are lots of back crossing as well.
 
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