Nit: grasses are a distinct genetic lineage, the Poaceae family. There are a few other linages outside of Poaceae that have convergently evolved to look like grasses, sedges and rushes, but they all fall in the same clade, Monocots.
Trees, on the other hand, are a growth habit, exhibited by species in a wide variety of plant families, even grasses (e.g palm trees).
Trees, on the other hand, are a growth habit, exhibited by species in a wide variety of plant families, even grasses (e.g palm trees).