Question
I have two peach trees.  The red one is fairly large but under control (in my back yard) in a large box I constructed.  I get good sweet fruit from it.  I have a small white peach tree in a 1/2 barrel container that has produced about a dozen peaches after thinning but year after year the peaches have a somewhat bitter taste.  What can I do to get sweeter peaches from this tree?  This is the second white peach tree that has had this problem.  I live in the SF Bay Area but out of the fog zone and spring and summer temperatures are good for growing, but of course the winter is not that cold.  Thanks for any help you can give me.  Leonard

Answer
I would suggest you take more care in ripening the peaches. When the peaches are let to ripen naturally, they produce their own sugars in the process. If you don't give the peach the right conditions, and time to produce these sugars, it will indeed, be bitter, and hard.
Try this: Place the peaches carefully in a paper bag, close it, and place it on the counter, or in a cool ( no cooler then 50 degrees) place. DO NOT PLACE IN THE REFRIGERATOR. This will halt the ripening process, and may make the fruit  mealy, bitter, dry or tasteless.
Never store in a plastic bag, as this may hasten decay. Also keep away from direct sunlight, as heat will damage the fruit.
Check to see if they are soft, and have a peach aroma. Use the flat of the palm, and not the fingers to check softness. This will prevent finger bruises. Depending on how ripe they were when you put them in the bag, it should only take one to three days. When the fruit is ripe, you can keep it in the refrigerator for a week or so.
Some ways to judge when the peach is ripe is to check the following:
Yellow under color
Peachy aroma
Tender flesh
Heavy
Well defined crease.

There isn't anything that you can add to the soil, or the growing conditions that will influence the peach flavor.
Some varieties don't have as good a flavor as others. This is a common complaint about dwarf peach trees. They were bred for tree size, and not peach flavor.
In baking a cobbler, or pie, you might mix the red peach, and white peach. The two flavors might balance each other and make for the perfect combination. I think of this because I like to mix rhubarb, and peaches for that balance of sweet and sour.