grass is fairly green; assume you are not in drought.

Maybe it seems that way, but my grass is TERRIBLE. Every year it gets a little worse but this year it's especially bad. I've always attributed it to the oak tree soaking up all the moisture in the yard..

I'm really hoping this isn't oak wilt. Idk though because there are two oaks just like it that are within 100 feet and they don't have this problem :/

so are you in drought or not ...

ken

I'm not sure what constitutes an official drought, but it's been very dry for the last month, yes.

Bingo, the tree is shutting down for the season due to insufficient soil moisture. Not unusual during very dry growing seasons. It's the tree's way of preserving its life for a, hopefully, wetter growing season ahead.

Approximately, where in North America are you (assuming this continent)..., we don't need a street address.

Harrisburg, PA...the only thing I'll say is, there are a few oaks just like it, same size...within 100 feet and they don't have this problem..

I always enjoy followups so I'll provide one. Seems I was right as something is definitely going on with this tree. The tree leafed out normal in the spring, and was fine up until about the same time this year, as last year. It is a pin oak and there are pin oaks all around my neighborhood that are still 100% green. Based on research I believe it is actually bacterial leaf scorch that this is plagued with. This is mine as of today.. Will probably remove in the spring, which sucks because it's an amazing tree with great shape. Btw that blue pot at the base of the tree is 30" in diameter for scale. Sucks...I believe the tree to be about 80-90 years old.

I sure wouldn't take the tree down yet without seeing another spring. It may just leaf out normally.

Yes...it WILL leaf out normally. That's what bacteria leaf scorch does. And gets worse each year. It was bad last year...worse this year...and will be worse yet next year.

"The first noticeable symptom is premature browning of leaves in mid-summer. Symptoms worsen throughout late summer and fall. Leaf margins turn brown, beginning with the older leaves and moving outward, spreading to leaves toward the branch tip. In most, but not all infected trees, browned, dead areas of the leaf are separated from green tissue by a narrow yellow border. The browned leaves may drop from the tree. Infected trees leaf-out normally the following year, with leaves on a few more branches turning prematurely brown in late summer. Symptoms become progressively worse over a period of 3 to 8 years, until the entire tree turns brown prematurely. The lack of green, chlorophyll producing leaves year after year leads to twig, branch, and limb death due to continual defoliation."

Yeah, I doubt dryness is the reason -- Harrisburg has avg rain for the yr. Short-term dryness isn't going to affect a mature oak like that. jalcon is prb'ly right -- leaf scorch, as this afflicts pin oaks.