This is something I have observed every summer but don't know what it is. They max out at 1.5" in diameter and the picture shows two that just fell after a thunderstorm, and others that have been on the ground for several days. They turn brown and shrink when they are left on the ground. What are these "things"?

Looking forward to seeing an answer to your question. We get those here as well.

Not sure, but could it be oak gall? Here is just one of the many articles about the oak gall wasp.

http://www.missouribotanicalga...

Yep, you nailed it, Vickie. It is the oak gall.

My daughter and her husband had to cut down an oak tree this year because it was infested so badly.

It must have been really bad and/or the tree was in decline. Everything I have read on the galls said that nothing needed to be done and that it was very unusual for the galls to do any significant damage.

Yes, it was really, really bad. It was in their back yard by the fence in their subdivision. We had a very bad drought in 2012 and I heard that the stress caused by drought can cause trees to die years later. Maybe the stress of the drought and the oak gall together was its demise.

Perhaps it was the combination, Vickie. All my trees are very healthy. One does not even see these (marble-looking) galls up in the trees. I only find them on the ground. You can see the rock-hard galls attached to some of the small lower limbs. If I can easily reach those on a ladder, I will snip off that branch just below the gall and throw the branch/gall in the trash. I have bee assured by a PhD tree expert that even the hard galls cause no damage, but I remove them for esthetic purposes.

You can usually ignore the galls. I don't like the look of them; but I've read that they're harmless, as Ken said.

Ken,
Well those are neat when they first fall, but are pretty ugly on the tree.

Vicki,
Thanks for the link. I didn't see it written, if the wasps were beneficial?

Sally, I am not sure if they have any benefits at all.

They might help pollinate plants but don't know that for sure. I just know the wasps are not harmful to humans.

Speaking of which. Do you know why fiddle leaf ficus (fig) plants are only found in only a handful of places in the world? They are pollinated by a single, specific wasp only found in those areas. So wasps can be beneficial.

Interesting Ken,
With the decline in honeybees we might be depending on other pollinators someday.

That is probably already happening in many areas, Sally.

Ken,
I know. I was amazed to have any apples last year. We did not see any bees on the tree in the spring. I don't know when it was pollinated, but we had a lot of apples!

Perhaps nocturnal moths, Sally. But I guess there are hundreds of insects with the capability to pollinate.

Yes, as long as plants aren't too specialized so only a few can reach, get hit on the back with pollen or whatever the plant needs.

There are branch galls that can harm or kill a tree if heavily infested but that is not what you have Ken,