Legumes are plants of the Leguminosae family that bear pods containing one or many seeds. The pods vary in size, color, and shape. They dehisce (split open) at both sutures which influences the probability of shattering during harvesting. Leguminous plants have roots that act as hosts for nodule-forming bacteria of the genus Rhizobium. The inflorescences of legumes are flower clusters and can be umbels (white clover), spike-like racemes(alfalfa), or racemes (field pea). Legume leaves are very different from those of grasses. They may be pinnate, meaning the central leaflet has a longer petiolule (stem connecting leaflet to petiole) or palmate, meaning each leaflet has the same length petiolule. The leaflets may have very distinctive watermarks, which may vary according to climate, but can be very useful in the identification of legumes.


Types of Legumes
Legumes can be annual, biennial, or perennial and are dicotyledons, which mean they emerge from the soil with two leaves. Whether a legume is an annual, biennial, or perennial will determine many forage-related decisions. Annual species mean annual reestablishment costs and labor. This also may lead to erosion hazards. Most annuals grow during the spring and summer but some legumes are winter annuals and when used carefully can add flexibility to a grazing system. Summer annual legumes can extend the grazing seasons and reduce winter feed costs. Perennials have inflorescences on some stems but also produce vegetative tufts which will wait for two years or more to produce an inflorescence. Perennials reduce the yearly cost and labor of reseeding but must be managed to thrive or may not be as productive.

Legumes are also grouped into cool season (C3) and warm season categories (C4). C4 and C3 plants both utilize photosynthesis which is a chemical process in which light energy from the sun is captured and mixed with water and carbon dioxide to make sugars which are used as food for chemical energy. C3 and C4 plants use different leaf anatomies to carry out photosynthesis. The differences are reflected in how plants take carbon dioxide from the atmosphere and use the components for plant functions. But it should be noted that photosynthesis also is influenced by solar radiation, temperature, water stress, and mineral nutrition.

C3 plants have an optimum temperature range of 65-75 degrees F. Growth may begin when the soil temperature is 40-45 degrees F. C3 plants become less efficient as the temperature increases but have higher protein quantity. The lower temperatures in early spring also affect the existence of other organisms so C3 need nitrogen in the spring because of low microbial action in the soil. Annual C3 legume plants include arrowleaf clover, ball clover, berseem clover, vetches, and black medic. Perennial C3 legumes include alfalfa, alsike clover, birdsfoot trefoil, and white clover. The degradation of C3 plants in the rumen of an animal is often faster than C4 plants because of the thin cell walls and leaf tissue and are therefore often of higher forage quality.

C4 plants are more efficient at gathering carbon dioxide and utilizing nitrogen from the atmosphere and recycled N in the soil. They also use less water to make dry matter. They grow best at 90-95 degrees F. They begin to grow when the soil temperature is 60-65 degrees F. Forage of C4 species is generally much lower in protein than C3 plants but the protein may be more efficiently used by animals.

Additional Information on Legume Types


Legume Species & Cultivar Selection Strategies

(needs legume specific information)

Strategies for optimal selection of legume species and cultivars involve identifying primary intended use, level of management, and climate and soil tolerances and local conditions.

Intended use. Identifying the primary use is a good starting point. Legumes may be used for forage (as hay, silage, greenchop, or pasture), for soil conservation or improvement, or as amenity species (as athletic turf or beautification).

Single species or mixtures. The relative advantages of pure stands and mixtures should be considered and the relative combining ability of the various species. Mixing species with vastly different tolerances will make management more difficult.

Management level. Management level should be considered, since species differ in their tolerance to low levels of fertility, defoliation schedules, and pests. Personal and professional goals and managerial experience and capability should be considered when selecting a management level that best fits your situation.

Climate and soil conditions. Matching your climate conditions (precipitation amount and distribution, and extremes of temperature) and the characteristics of the soil (drainage, fertility, pH, and salinity) to the species you intend to plant is fundamentally important. Knowing the long term averages and year-to-year variability in climate conditions and the major soil types and characteristics will help you choose species with a high probability of success. Legumes are particularly sensitive to pH levels and drainage conditions, so special attention must be given to these characteristics.


Legume-related Resources