Why Do I Have Fruit On The Graft If My Satsuma Tree

Question

The satsuma has fruit too

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Answer 1

likely, the graft was near fruiting age when it was installed. This will be the reason for grafting, typically, so that you can get fruit much faster.

https://www.gardeningknowhow.com/edible/fruits/tangerine/mandarin-orange-tree-care.htm

https://www.gardeningknowhow.com/garden-how-to/propagation/grafting/multiple-grafted-citrus-trees.htm