However, a few trees, such as cottonwoods, oaks, and willows grow in river valleys, and some nonwoody plants, specifically a few hundred species of flowers, grow among the grasses.    From Wordnik.com.  [Grassland biome] Reference

These include dominance by woody, broad-leaved, deciduous plants, nonwoody plants with underground storage structures and spring blooming (1,400 species in the Great Smokies alone), early-leafing ephemeral herbs or shade-adapted perennials with buds that overwinter, and plant communities that vary predictably along environmental gradients.    From Wordnik.com.  [Appalachian-Blue Ridge forests] Reference

The vegetation at that time consisted of nonwoody plants.    From Wordnik.com.  [Red Hispanic - A Townhall.com user blog] Reference

Herbaceous refers to the fact that a plant has a soft or nonwoody stem.    From Wordnik.com.  [WN.com - Articles related to Invasive plant killing Dartmouth lake] Reference