Bitter citrus fruit

[huffyboy]

I have 2 very tall & mature orange trees. The oranges are very healthy and plentiful yet they have an undesirable taste. Are there any fertilizer options to make the fruit sweet or is grafting the only way to remedy this problem? Thx, MH

 

[Tank]

What kind of oranges are they? Fertilizer won't help. If you don't like them you could either graft on a more desirable variety or replace the tree with something better.