Question
Hi there,  I have a pomelo tree that bears a lot of fruits, unfortunately, the fruits are pretty small and crinkled, citrus fertilizer didn't help either. The fruit inside is  sour and bitter. The tree is about five feet tall and bears a great amount of flowers, the fruit would be the size of a large orange but crinkled. It matures to a bright yellow and then falls off.

What could be the problem.

Thanks!!

Tino

Answer
 Hi Tino...sounds like you lost your pomelo and now have a sour orange taking its place.  If you look at your tree you will see towards the ground a swelling on the trunk of the tree.  The swelling area is a graft where they place a tree on a tree.  If there is branches coming out from the graft area (lowest to the ground) it will take over your pomelo and kill it, turning your tree into a sour orange.  Nothing you can do will change it back into the pomelo as it is long gone.  So when you replace it with a pomelo be careful to watch the graft area so it doesn't happen again to you..