Minecraft wiki entry for Survival_in_an_infinite_desert, associated text: If you are using Buffet world generation rather than superflat world generation, a river biome may appear along internal borders between two Desert biomes [needs testing in 1.14]. If this has a low bank, it may allow grass and/or flowers to spawn (as the grass is still in the “River” biome). The grass blocks can be 'grown' by adding adjacent dirt blocks, and the growth of flowers and tall grass can be boosted with bone meal.