I have a tangerine about 12 years old in a container. It's outside in summer, indoors in winter. It has tons of flowers, buds and fruits all the time, but they're sour! What can I do to sweeten the fruit on the tree?
I'm in Charlotte, North Carolina. It's no particular variety of tree, just seeds from a tasty snack that germinated. I heard wood ash could sweeten them but had no effect. The tree is very lush and smells heavenly.
It seems as if you're saying you grew your tangerine tree with a seed you saved and planted from a fruit you'd eaten. The thing about citrus trees is, they will grow from seeds gathered in this way, but you never know what the fruit's going to be like, or even if it will fruit. Yours obviously is fruiting very well, but unfortunately, the fruit is sour. You can't do anything to sweeten it, that's just what you happened to get from the seed you planted.
To be sure of getting tasty and edible fruits, most citrus are vegetatively propagated rather than grown from seed.
Aside from the coping mechanism I've made a comment about of sweetening off the tree in "tangerine products", the only way to get sweet fruit off your tree is to graft a sweeter variety onto your tree - effectively using your tree as a rootstock and changing the variety of fruit (and thus its sweetness on the tree.)
