Berry cultivation has long been known to Unova from international trade, but has never been practiced successfully in that land. This is because of the Pansear, fire-type monkeys who not only gleefully eat berries, but fanatically incinerate any which they cannot devour. It is unknown why such a behavior developed in the Pansear, for whatever evolutionary benefit it allowed them must have been marginal at best; although a berry can be advantageous in a pokemon battle, the wanton destruction of these trees destroyed Pansear's own supply as well as those of their enemies, and they incinerate berry trees even at the risk of their own life. But the often foolhardy tenacity with which Pansear ruin berries was successful in making berry farming uneconomical at best, and life-threatening at worst; for this reason, Unova never developed an indigenous berry industry.
Most Unovan pokemon trainers, and a few devoted fruit eaters, instead rely on the so-called "Dream World" for their berries; a mysterious place where the wild Pansear of our world, who climb over and around every barrier created by man, are unable to enter. Scattered reports describe a very different species of Pansear which inhabit this land, who treat berries no differently from any other held item, although they can be taught to incinerate those held by their foes in battle.
In this urbanized era, wild Pansear are few and far between, and a few have proposed turning over portions of Unova to berry cultivation. But the memory of the Pansear looms large among farmers, even in parts of Unova which have not seen one in a hundred years, the loamy soil which berries crave has been replaced with dirt more suited to other crops, and in much of Unova, agriculture has been replaced outright by skyscrapers.