I have a peach tree but the fruit is very small and doesn't mature. I need to know what I can do.
Care for Peach Trees
Certified GKH Gardening Expert
The two key things will be pollination and phosphorus. Do not use any kind of pesticide, at least until the fruit starts to appear, so that plenty of pollinators will go to the flowers.
Add a phosphorus rich fertilizer to the soil. This will ensure that the fruit develop well. Potassium does not hurt either. But be careful not to add too much nitrogen.