When will my grapefruit start to grow? A lot of them split open at the bottom before they ripen. Why?
Citrus splitting is not uncommon, although grapefruit suffer from the condition much less often than other citrus. It is caused by uneven watering, usually a certain amount of drying, which causes the fruit to shrink, then large amounts of water, which causes fruit to swell faster than skin can grow. While you can't stop the rain, you can water when there's a drought. This article has more information: https://www.gardeningknowhow.com/edible/fruits/oranges/oranges-splitting.htm