What is This Weird Fruit?

Factual Questions
1

I was cutting back some shrubs in the yard, and encountered a very strange fruit.
These are like small yellow apples-about 2 " in diameter, and extremely hard-I had a tough time cutting on in half. I tasted the thing, and it was very sout. It grew on a shrub that had thorns on it-and leaves that looked a bit like apple leaves.
Anybody know what this thing is?
I could not find it in a book of N American trees.

2

Can you provide photos of the shrub and the fruit.

3

Quince?

4

“What’s this weird fruit” questions often turn out to be Osage Orange.

5

I thought the same thing as soon as I read the thread title (though I was thinking Hedge Apple). But normally when people find one they either have a picture are describe it in more detail the the OP since it’s so unusual looking.

6

Interesting. Never heard of it. But the OP should take note of this before eating strange unidentified fruit:

Is this fruit difficult to cut into? I immediately thought quince because it’s extremely hard to cut and has a sour and astringent flavor.

7

Interesting tree. I especially like this trivia factoid:
When dried, the wood has the highest BTU content of any wood, and burns long and hot.

8

Maybe Poncirus trifoliata? Has little yellowish ‘fruits’ and has rather prominent thorns as well. Is known to spread easily, too, so it can ‘volunteer’ in obscure areas, ime.

9

You nailed it! Are these “fruits” edible?

10

Is this what it looked like on the inside?

If so, it appears not to be so good to eat.

11

We have a few bushes of those growing at work, I have wondered for the past seven years what they could be.

12

Oh, it’s Ponzu!

13

Let’s hope it’s not the strange fruit in the song.

14

Wikipedia says it can be safely made in to marmalade.

15

It is considered invasive in many parts of the United States. Invasive Listing Sources:

* Mid-Atlantic Exotic Pest Plant Council, 2005
* Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
* Reichard, Sarah. 1994.  Assessing the potential of invasiveness in woody plants introduced in North America. University of Washington Ph.D. dissertation.
* WeedUS - Database of Plants Invading Natural Areas in the United States
* Alabama Invasive Plant Council
* Georgia Exotic Pest Plant Council Category 3
* South Carolina Exotic Pest Plant Council Significant Threat
16

Are the fruits of Poncirus trifoliata that hard to cut? The OP’s description still sounds more like a Chaenomeles quince to me - in photographs, the two plants, with their fruits, look superficially quite similar*, but I’d have thought the ‘apple’ part of the description fits a quince better.

*For example: this

17

I agree. The Poncirus trifoliata looks like a citrus fruit in texture, which is partly why I posted a picture of the inside cross-section of it in a follow-up post. Quince is hard as a rock to cut through.