Written by Rachel Frost, Montana State University
Grasses are plants with jointed stems. The stems are normally hollow between the joints (node). Leaves are in two rows on the stem. Veins in the leaves are parallel. Grasses are generally the most important and abundant kind of range plant for grazing animals.
Forbs are broad-leaved plants with aboveground growth that dies back each year. Most forbs have net veins in the leaves, but a few have parallel veins. Broadleaf weeds and wild flowers are examples of forbs.
Grass-like plants look like grasses but have solid, though not hollow, stems without joints. Stems may be triangular. Veins in the leaves are parallel. Sedges and rushes are in this group of plants.
Trees and shrubs are plants with persistent woody stems that live from one year to the next. Shrubs have stems that branch from near the base, while trees have a definite trunk and are usually bigger than shrubs. Some plants can take on a shrub or tree growth form, depending on environmental conditions.
Weed is a designation that can be given to any plant that grows where it is not wanted or interferes with the growth of desirable plants. The term "weed" is usually reserved for plants that have a persistent and aggressive growth habit.