Here are the leaves from the top:

Not sure. Spider mites cause a "sprinkling" of pale dots, but not quite like that.

I wouldn't worry, oaks have endless leaf predators (including bacteria & fungi), but other than gypsy moths, not usually serious because there are predators of the predators -- including predatory mites that attack the spider mites.

Looks like a combination of nutrient deficiency (this can weaken a plant), and weather favoring some secondary pathogen. Our larger Scarlet has some similar leaf spots, but they have not grown since early in the spring. Now as for what nutrient? No certain way to know without complete analysis of the leaves versus analysis of wild healthy leaves. You can get some indications from the pattern (will need to Google nutrient deficiencies) can help narrow it down a bit. Still, you are left with a shotgun approach. Even then it may not reverse. I periodically see these kind of problems, and is one of the reasons I fertilize pot grown seedlings every few weeks during summer.

Arktrees

I wouldn't be concerned either. It does appear there's a mineral deficiency whether iron or magnesium (likely) I don't know which. And probably some bugs causing the stippling.

Dax

I'm fertilizing these as well, and the other Q. coccinea seedlings (in exact same potting mix, container type) are not showing this trait. They are a foot apart and get the same amount of sun, moisture, etc...

Looks a bit like chlorosis from high pH as well, but the mix they're in is fairly acidic, so I don't think that would be it.

We did have a wet couple days as those leaves were expanding, but it doesn't look like anthracnose, either.

Just seems odd that only one of my three remaining Scarlets is doing this (I had more but gave away a couple and culled a runt).

I have 2 old scarlet oaks in my garden (pic of the top of one in the background from last Nov attached) - I think my DH's grandfather planted them. Very rare on the West Coast, of course - I believe they are native to the US East Coast?

Just curious, as I know nothing about trees - are those of you who are growing seedlings in pots working for nurseries, or planning to plant forests? Thanks for the info. I love these trees - you can see them from all over our neighborhood in the Fall.

Jackie

I'm just doing it for my own use. I'm opting for pots vs planting directly in the ground for a few reasons...one, I can select only the "best" seedlings for planting in their permanent location, two, they're most likely for a property (several acres) we haven't purchased yet but will within a year or so if things pan out.

Hair,
Individual genetic variation. If some mineral is marginal, then some will show signs, others will not. Just as you have variation in growth, fall color, etc. Plus there may be some microbial factor (i.e. mycorrhizae), or tiny micro-climate difference. Two genetically identical twins can have significantly different microbial communities despite living in a near identical environment. Sometimes it just happens.

Jackie,
Nice looking trees. I grow various species and give them away. I do it because I want to do so. I try two or three species each year, usually something I have not tried before. I get to experience other species this way that I would not have room for, and get to make sure people I know plant something other than crap callery pears. I have also given several away in honor of new kids, house warming, and weddings. These usually go over very well, and serve as a reminder. New infant trees to grow up with new infant children especially so.

Arktrees

Maybe I should throw something with "micros" on it like Foliage Pro...

I noticed something similar on 1 of my Q. Boicolor and a few of my red oak family oaks Shumard, Nuttals. It may go away itself. My Durand oak had some crunchy new growth. IOW, the top inch of new growth is dried out. I think ,maybe some good rain will help mine, do you need some rain HairmetalF ? You will be getting it from Aurthur right? I am guessing it will affect you with rain. I am hoping for a ton of rain tonight. We need it because of the high 80"s and 90's we've had for a few days straight. I watered the new transplants a little today, if it doesn't rain tonight ALOT, I will be out there dragging the hose around. I say about new growth, because the leaves below look much greener, on your seedling.

We've been OK on rain this year - a surplus for the year, but somewhat drier (although near normal) in June.

If anything these are probably erring on the side of too much water, but are in a very, very, very well-drained potting mix so should be OK.

The roots looked good when I potted them up a few weeks ago - no rot/soft areas, etc, so I don't think that's the issue.

We might get showers on Thursday from Arthur, but there will also be a cold front causing some showers/storms tomorrow and Thursday.