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They are found in savannahs. It's a way to survive the frequent fires that occur in grasslands

In fact every.tree.has an underground tree in form of its roots;)

No, these are a specific type of tree, called geoxylic suffrutices

Ah yes I see. Went for a google research and found that there is a goxylic suffrutices with the same ganus as the persimmon (dyospyros lotus) which i can recommend to try if you haven't already.

I love persimmons!