Clover, or trefoil, refers to herbaceous plants belonging to the genus Trifolium (pea family, Fabaceae). These plants are characterized by leaves typically featuring three leaflets, which is the source of the genus name (tres meaning three, folium meaning leaf). Clover is recognized globally for its agricultural and ecological value, thriving across temperate and subtropical regions. Its ability to host symbiotic bacteria (rhizobia) in root nodules allows for atmospheric nitrogen fixation. This process converts nitrogen gas into a usable form, enriching the soil and making clover important for forage, green manure, and cover cropping systems.
The True Count of Clover Species
The genus Trifolium contains approximately 300 species worldwide. These include annual, biennial, and short-lived perennial plants that share the defining three-leaflet structure. While the exact count varies due to ongoing botanical research, Trifolium remains one of the largest genera within the legume family.
The highest concentration of species diversity occurs in the temperate Northern Hemisphere, particularly the Mediterranean basin. Other centers of diversity include western North America and the highlands of eastern Africa. Despite this extensive range, only a fraction of these species are widely cultivated. Most commercial and wild clover populations originate from a few dozen species introduced globally, leading to many becoming naturalized outside their native ranges.
Identifying Major Types
Among the hundreds of species, three types of clover are most commonly encountered in pastures, lawns, and agricultural fields globally.
White Clover (Trifolium repens)
White Clover is a low-growing, perennial species recognized by its creeping growth habit, spreading via above-ground stems called stolons. Its small, ball-shaped flower heads are typically white, sometimes tinged with pink. The leaflets often display a pale crescent-shaped marking.
Red Clover (Trifolium pratense)
Red Clover is a taller, more erect plant that functions as a biennial or short-lived perennial. It lacks the creeping stolons of White Clover and features larger, hairier leaves. It produces dense, oval-shaped flower heads that are a distinct purplish-pink color. Red clover is primarily cultivated for hay and forage due to its upright growth, despite having a shorter lifespan of two to three years.
Crimson Clover (Trifolium incarnatum)
Crimson Clover is an annual species known for its spectacular, elongated, scarlet-red flower spikes. This clover grows upright, reaching heights of up to 1.5 feet, and is covered with soft, light-green hairs. It is frequently used as a winter cover crop and green manure because it is an early-maturing species with excellent seedling vigor.
What Looks Like Clover But Isn’t
Many plants that are not true clovers share the characteristic three-leaflet structure, leading to frequent misidentification.
Wood Sorrel (Oxalis)
Wood sorrel is perhaps the most common imposter found in lawns and gardens. While it has three leaflets, they are distinctly heart-shaped with a deep notch at the tip, unlike the rounded or oval leaflets of Trifolium species. The flowers also provide a clear distinction, as wood sorrel produces small, single flowers with five separate, identical petals, often yellow or pink. True clover flowers, conversely, are clustered tightly into dense, bushy heads composed of many tiny, tube-shaped florets. Additionally, wood sorrel produces small, okra-like seed pods that explosively disperse seeds, a feature absent in true clover.
Sweet Clover (Melilotus)
Sweet clover is another common group often confused with Trifolium. These plants are related to true clover but are generally much taller, featuring slender, elongated spikes of white or yellow flowers. While the name suggests a connection, recognizing the difference in leaf shape, flower arrangement, and overall growth habit is necessary for accurate plant identification.