Grass is the most common plant found in Runeterra. Its abundance is however dependent on each region. For instance, there is more grassland in Demacia then around Noxus Prime. This is because of Noxus' infertile soil. The climate of a region also comes into play. Most of Freljord has a climate far to cold for any grass to grow.
In Ionia, quite literal rivers of grass, flow and move with the tides of magic. Landfishers, if intinued with the magic of the landscape, can cultivate and collect all the grains and fruits that grow in these areas.