Why are some grapefruit rinds thick and some thin? What causes that? Is it true that the fruit will be tart on tree with thorns?
Certified GKH Gardening Expert
Very simply, a thick peel on any kind of citrus fruit is caused by a nutrient imbalance. You can read more about this here: https://www.gardeningknowhow.com/edible/fruits/citrus/citrus-fruit-thick-rind.htm
And, no, the presence of thorns is not an indicator of a fruit's tartness or sweetness.