Sweet clover (Melilotus species) is a versatile plant with a long history of widespread use in agricultural and ecological settings. Both yellow (Melilotus officinalis) and white (Melilotus albus) sweet clover varieties are recognized for their beneficial properties. Originating from Europe and Asia, sweet clover has become naturalized globally, adapting to diverse environments and proving a valuable addition to many land management practices.
Benefits for Soil Health
Sweet clover enhances soil health. It is a nitrogen-fixing legume, enriching the soil with nitrogen via a symbiotic relationship with root bacteria. These bacteria convert atmospheric nitrogen into a plant-usable form, benefiting subsequent crops. It can contribute substantial nitrogen, up to 100-200 pounds per acre.
The plant’s extensive and deep root system improves soil structure. Its taproots penetrate compacted soils, sometimes reaching depths of 5 to 20 feet, which aerates the subsoil and improves drainage. As the plant decomposes, its deep root system and biomass contribute organic matter to the soil. This organic matter improves soil tilth, increases water absorption, and enhances nutrient-holding capacity. Its robust root network also helps prevent soil erosion, particularly on sloped or disturbed land, by stabilizing soil particles and reducing runoff.
Benefits for Pollinators and Wildlife
Sweet clover benefits pollinators and wildlife. Its flowers attract bees, especially honeybees, and other beneficial insects. The plant’s scientific name, Melilotus, derives from Greek words meaning “honey” and “lotus,” reflecting its historical recognition as a significant honey plant. It produces abundant nectar with a high sugar concentration, often averaging around 52%, beneficial for honey production. Its long flowering period, with yellow varieties blooming earlier and white varieties extending the season, provides a consistent nectar and pollen source for several months.
Sweet clover also offers cover and food for small wildlife. Its foliage and stems are a food source for animals such as elk, deer, and antelope. Its dense growth provides nesting materials and protective cover for various bird species and small mammals.
Benefits as Livestock Forage
Sweet clover is a nutritious forage option for livestock. It offers a good source of protein, with crude protein content typically around 15% in its early bloom stage. The plant is palatable to animals, particularly in its vegetative to bud stages, though palatability decreases as stems become woody with maturity. It can be utilized for direct grazing or harvested for hay and silage.
When used for hay, proper curing is important due to coumarin, a natural compound in sweet clover. If sweet clover hay becomes moldy, coumarin can convert into dicoumarol, an anticoagulant that interferes with blood clotting in livestock. To mitigate this risk, hay must be thoroughly dried before baling. Low coumarin varieties are available, and managing grazing to prevent bloat, similar to other legumes, is a consideration.
Other Practical Advantages
Sweet clover offers practical benefits. Its rapid growth and dense canopy suppress weeds by outcompeting them for resources and sunlight. While a poor competitor during its establishment year, a well-established stand effectively controls weeds during the fall and spring.
It is frequently used as a green manure, a cover crop tilled into the soil to enhance fertility. As a green manure, sweet clover contributes organic matter and nitrogen, improving soil quality and tilth. Its deep roots also scavenge essential minerals like phosphorus and potassium from deeper soil layers, making them accessible to other plants. Sweet clover is resilient in drier conditions once established, exhibiting good drought tolerance, making it suitable for areas with limited water availability. In more specialized applications, sweet clover shows potential for bioremediation, aiding in the cleanup of contaminated soils.