I was searching the web for the name and author of the story about the Yanda tree, and found the answer on this site (I didn't ask the question on this site, a Google search found my keywords here). How about one more old scifi tree-oriented story I'd like to find again ? As I remember there were no humans or creatures of any kind in the story, other than two forests that had a nuclear war with each other by gathering natural uranium deposits and using their prehensile roots to place critical masses beneath each other.
Could this be "[The] Process" by A.E. Van Vogt?
A sentient forest challenges arboreal neighbors and a spaceship that has landed among its' woodlands, which soon departs after being warned away with micro-mined uranium ore
Shortly after dawn the following morning, it launched its attack. Its victim was the forest which - according to its faulty recollection - had originally invaded its territory.
Along the entire front which separated the two colossuses, small atomic explosions erupted. The solid barrier of trees which was the other forest's outer defense went down before blast after blast of irresistible energy.
The enemy, reacting normally, brought up its reserve of sap. When it was fully committed to the gigantic task of growing, a new barrier, the bombs started to go off again. The resulting explosions destroyed its main sap supply. And, since it did not understand what was happening, it was lost from that moment.
Into the no-man's-land where the bombs had gone off, the attacking forest rushed an endless supply of roots. Wherever resistance built up, there an atomic bomb went off. Shortly after the next noon, a titanic explosion destroyed the sensitive central trees - and the battle was over.