I will preface this by saying I have no idea what I am doing when it comes to fruit trees so this is a long post. I just pick the fruit that grows in my yard when it looks ripe or starts falling off the tree. We didn't plant the trees, so I don't know what varieties any of the fruit are, and I have basically no knowledge when it comes to purposefully growing fruit.
We live in Prescott, Arizona, so not too brutally hot during the summer, and early in the summer we had a very good rain season (almost every day in July!) We have 3 peach trees in our yard that were planted before we bought the house, but I think are probably 8 years old or so (plus one dwarf peach tree). We also have 3 plums, a cherry, 2 pears, 2 apples, and one apple tree that has grafted branches and so I have no idea what is on it! However, this is about the peaches ...
One of these peach trees has produced fruit almost every year we have lived here, I call it the "good" tree. Some years they are fuller and juicier than others, but there is almost always something there.
This year the peaches were just fantastic! ... but only on half of the tree! The first half of the tree ripened nicely. And while the very last (and biggest) peach was juuuuust getting ready to be plucked ... a passerby stole it off the tree! I was devastated since I had been saving that one!
But, that is beside the point ... just as that last one was getting perfectly ripe and was fist size, the second half of the tree was chock full of peaches that were maybe 1-1.5 inches in diameter and green. I was thinking since that half of the tree had a separate trunk it was just maturing later in the season, although I don't recall that pattern in years past.
Well. Now all these "unripe" peaches are still only 1.5 inches in diameter, and are green, and yet they are falling to the ground and are somewhat soft! So, I tried one. It tasted somewhat under-ripe and tangy, but the flesh was soft and fairly juicy. Also, the meat was WHITE! and it stuck to the pit severely. The first half of the peaches had meat of a lovely yellow-orange and all plucked right off the pit.
Is this due to not enough water, somehow? Even though it is the same tree? Is it possible to have different varieties of peaches on the same tree? I am so baffled, this hasn't happened before on this tree.
The other 2 of our trees have never produced fruit until this year, I think due to peach curl and various insect infestations. This year, both of them produced peaches! (Also, 3 plum trees that never have produced before put out crazy amounts of very tiny plums!) On one peach tree, all the peaches prematurely shriveled up and we were unable to harvest any fruit from it (It didn't get much supplemental water, I think).
On the second tree, the peaches were much like the ones on the second half of my "good" tree - quite small, skin light yellow or green with maybe a hint of ripe color, flesh completely stuck to the pit.
Again, not sure of the varieties that were planted, and since two of the trees never produced fruit before I have nothing to compare those to. However, on the one "good" tree, how is it that half of the peaches were so drastically different? The tree does not have insect issues. and is on a drip line for watering, when we remember to water it, and when we are in the HOT and dry season (June) leading up to monsoon season.
Any ideas what could have caused this under-ripe half of the tree? I assumed the little green things would grow up to be as lovely as the rest, then one day my driveway was full of tiny peaches that had fallen and scattered everywhere!
Please help, I am so curious as to other folks' experiences that may be similar to this one.
Thanks,
Steph
Steph,
Welcome to the forum. Growing fruit can be a challenge. Congratulations on harvesting a bunch of good fruit with minimal planning.
For your peach tree that is half good and half bad, the very probable explanation is that it is a grafted tree, as most worthwhile cultivated fruit trees are. That means that the top of a tree variety known for producing good fruit is spliced onto the bottom of a tree that provides good roots.
Normally everything above that graft union, where there are spliced together, is the genetics of the chosen fruit variety, and everything below is the rootstock. Sometimes the rootstock will send up suckers from below the ground, or a bud will grow a trunk from the rootstock.
In that case, any fruit that is born on the growth that can be traced down to the rootstock without passing the graft union will be of the type that the rootstock makes. Rootstocks aren't chosen for having good fruit. Most fruit trees aren't suitable for making good fruit. That's why the good ones are celebrated and reproduced by grafting.
Sometimes you'll get lucky and the fruit from a rootstock, or seedling, will be worthwhile or better.
Welcome, both 
Steph wrote: “I was thinking since that half of the tree had a separate trunk it was just maturing later in the season, although I don't recall that pattern in years past.”
I also agree with Jafar’s description, and your statement above seems to confirm there are ‘separate trunks.’ I’d follow the small-fruiting branches down it’s trunk … to see if it originates from above or below a ‘knotted’ or obvious graft union. If the small-fruited trunk emerges from below the soil, and is not connected above the ‘knot’ at the base of the ‘good-sized’ fruiting portion, it is likely (as described) a rootstock ‘shoot’ that had not been removed…
If that’s what you find, I suggest waiting until next spring (during dry weather) and removing the ‘root sucker’ portion to the ground, as well as any future shoots it may push up.
Your remaining fruit trees sound like an asset to your home ..be careful though, nurturing them can be addictive 
Idyllwild
simplepress
jafar
Marsha H
Viron
John S
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