In general, persimmons turn orange color when they ripen. You can tell if the fruit ripen just by the fact that they stop getting larger. Fruit can stop getting larger and start a ripening process which could take several weeks. You don't say where you live, in zone 6 and lower, it could be Oct or even Nov before persimmons ripen.

There are two kinds of persimmons, astringent and non-astringent. Even the non- astringent ones could still have astringy if picked too early. Unripe persimmons can be very astringent. You won't forget the feeling when you bite into one.

Most likely American persimmon (Diospyros virgiana) based on small size. That means it will be the astringent type as rphcfb14 talked about above. These are incredibly delicious when completely soft-ripe.

The closely related Asian persimmon (D. kaki) is the larger one you often find in the supermarket starting this time of year, usually the non-astringent "fuyu" variety, which is eaten while still firm.

Some consider the Asian persimmon to be the most widely grown tree fruit, mostly because of its popularity in China and the rest of Asia.

I'm jealous that you happened on this fruit in your backyard, as I've been trying to grow them, but they are not doing well in my climate!

We have family in MO and the American persimmon do occur naturally unassisted by man. The fruiting is rather haphazard, varying from year to year. Sometimes it's best to wait for the first frost to make sure the ripening is complete and minimize the risk of biting into an astringent fruit, tempting as it may be.

Thank you all! It was a persimmon after we got a better look today! :-)

Ah, the old 'wait 'til after a frost' thing. It's an old myth that just won't go away. If you waited until after the first frost or freeze, you'd miss most of the persimmons here. When they're soft... they're ready; depending upon the individual tree, most drop when ripe, but some will hold their fruits til the point that they virtually dry on the tree.

Oldest, most productive grafted American persimmon I have in my orchard (NC-10 variety), is dropping ripe fruits, a gallon or more a day, starting around 10 Sept, every year. They'll all be long gone before we ever have our first frost.