The major plant families that are used as forages are: grass (Poaceae previously known as Gramineae), legumes (Fabaceae previously known as Leguminosae), forbs, shrubs, brassicas, and some trees.

Seventy-five percent of forages are grasses. Of the 10,000 grass species, about 40 are commonly used as forage. Grasses are usually herbaceous, which indicates that they produce a seed, do not develop woody tissue, and die down at the end of a growing season. They are annual or perennial. They are monocotyledonous which means one leaf sprouts from the seed, and they often have jointed, slender, sheathing (wrapping) leaves. Grasses can be large, like bamboo or corn, or small like annual bluegrass. Grass plants develop fruit called grain which feeds much of the world. Though the grain is valued by humans, grasses have green leaves and stems not digestible for humans that are the main food source for animals. Some grain is fed to livestock but the leaves and stems are the mainstay of animal feed. Grasses also can be used for building materials, medicines, and biomass fuels. Grasses are very widespread, adapting to many locations.

Legumes make up the second most common plant family used as forage. Of 12,000 legume species worldwide, about 40 are commonly used for forage. The area where legumes may grow is more restricted than that of grasses, and legumes often require more care or management to survive and be productive. However, legumes are important because they participate in a symbiotic relationship with nitrogen-fixing bacteria called rhizobium. These bacteria reduce (change) atmospheric nitrogen to a form available to the plant. Legumes, therefore, do not require as much nitrogen fertilizer, a costly item for producers to provide. They are often planted with grasses to provide nitrogen to the soil and to provide more protein, as legumes are higher in cellular protein than grasses. Legumes are dicotyledons, which means that two leaves emerge from the soil. Legumes can be annual, perennial, or biennial. They produce a pod as their fruit which is indicated by the name "legume". Legume means: a monocarpellary (one-chambered) fruit containing a single row of seeds which dehisces (splits) along both seams (ribs, sutures). There are thousands of legume species in the world but less than 40 are used commonly for forage. The legume family includes clovers, medics, and trefoils.

Forbs are herbaceous (not woody), broadleaf plants that are not grass-like. Grass-like plants include sedges (Cyperaceae) and rushes (Juncaceae). Forbs are herbs other than grasses. Examples include: comfrey, small burnet, and chicory. Sunflowers are becoming more popular as a forage forb.


Shrubs are low, several-stemmed, woody plants such as: tumbleweed (kochia), blackberry, and wild rose.

Mustards (Brassica) have been used to supplement livestock feed for over 600 years. Brassicas are biennials, producing a vegetable the first year and seed in the second but are usually used as annuals in forage-livestock systems. Some producers used to harvest the crop and feed it to the animals. Now, it is more common to see animals grazing the crop which does take a bit of practice on the animal's part. Some of the brassicas are used for their leaves and some for their root portions. The major examples include turnip roots; swedes which include common or oil-bearing rapes: and cabbages which include kales. (A cross between Chinese cabbage and Stubble Turnip has produced Tyfon.) Rape and turnips have regrowth potential. Brassicas are nutritious with high protein and energy capacity. Often these crops tolerate cold temperatures well and are used to extend the foraging season. In some areas they can be grown year round and do not demand a lot of cultivation. They do require much moisture but are intolerant of poor drainage. They are tolerant of several soil types.

Trees are known as woody, with one main stem and branches. But trees can also be shrubs or herbs with a tree-like formation (arborsecent). Leaves of some trees are foraged by livestock and wildlife. The acacia tree is often grazed by giraffes.