Oak seedlings are notoriously difficult, often with foliage markedly different from adults of the same species.

Can you perhaps get photos of the parent trees the acorns came from?

Resin

Thanks, Resin! I hope these photos provide the right details. By the way, I live in the Sierra Nevada foothills, 1600 feet elevation, 33 miles north-east of Sacramento, CA (if that information helps narrow it down).

Josh

{{gwi:375512}}
{{gwi:375513}}
{{gwi:375514}}
{{gwi:375515}}

Blue Oak Quercus douglasii

Yep, location and the photos helped a lot!

Resin

Ah, excellent! I had hoped they were Blue oaks!
Thank you very much!

Josh

Well, about a week ago, one of the oaks lost all of its leaves. I'd watered both the day before, then woke up to find that the oak in the light green monrovia container (left, in pics in first posting) had not a leaf upon it. No sign of animal damage, chewing or otherwise. Stem fully intact, including the original growth tip.

I must assume that the morning sun just blasted it....or something? However, the oak in the black plastic container, sitting right beside the other, wasn't damaged at all.

I made a small scratch, saw green, crossed my fingers, and moved both oaks to the north-east side of my house. Now, the oak in the black pot has pushed out about an inch of new growth. And it looks as though at least two small buds are turning red and swelling on the leaf-less oak.

Could it be that this second push of growth, which followed hot weather, pushed the old leaves out?

I'm just hoping the tree doesn't die.

Josh

Sounds a reasonable deduction to me. The second summer growth push on oak seedlings is often more vigorous than the first spring push, so if all goes well you'll get a lot of new foliage.

Resin

That's wonderful news, then! Thanks, Resin.
I'll snap some photos of the buds as soon as they break.

Josh

While the other oak recovers, this first year seedling is really taking off. Theoretically, there's only one acorn in the pot, so it'll be interesting to see what's happening with the roots. Maybe low damage encouraged a triple-stem; or perhaps an animal slipped an extra acorn in the pot? We'll see...

Either way, nice green growth!

{{gwi:375516}}

Josh

Sometimes a single acorn contains two or three embryos, I'd guess that's what's happened here.

Resin

The leaves show that this is probably a blue oak X valley oak hybrid. Typical blue oak leaves are smaller and lack clear lobing. Valley oak leaves are like those of white oaks.
Drive up further into the foothills away from the influence of valley oak and you'll see what I mean.

How much further into the foothills? I'm between Auburn and Grass Valley, seventeen minutes below Colfax, and just a few miles from the Bear River.

Thanks!

Josh

I think you'll find some nice blue oak/grass woodlands on 49 between Auburn and Coloma. Looks good at 60 mph, anyway!

Yes, I like it out that way, and I haven't been to Coloma for a while. Thanks!

I have a blend of oaks on my property as is, so I don't doubt that hybridization
is possible. I've seen it occur with other oaks not far from here.
_________________________________________________

Resin wrote:
"Sometimes a single acorn contains two or three
embryos, I'd guess that's what's happened here."

Will the stems fuse into a single trunk, or will they typically die off?

Apologies for the dark photo, but here you can see the new leaves and growth.
I'm beginning to second-guess my hypothesis....wondering if some creature
(deer, most likely) didn't just bite the top off. Of course, it could
be that the tip has simply dried beyond the point of telling. I'm
hoping that one of the lower buds will open....but we'll see.

Josh

{{gwi:375517}}