Trifolium is a genus of low herbs, stipules present. Trifoliums, and many other legumes (plants in the family Fabaceae), have root nodules that are symbiotic with Rhizobium bacteria. These bacteria have the capacity to take nitrogen (N2) from the air and convert it to NH4 (ammonium), which the plant can then use to make amino acids which are linked together to form proteins. This process is known as nitrogen fixation (Raven et al. 1986).
Leaves alternate, 3-parted (trifoliate), leaf stalk with swollen base (pulvinus) that assists in orienting the leaf surface, margin finely toothed (serrulate).
Flowers white to red or yellow, bilaterally symmetrical, pea-slower-shaped, calyx tubular strongly 2-lipped, with 5 pointed lobes; petals 5, the uppermost (banner, standard, or flag) largest and outermost, often folded over the side petals but with the outer end pointing upward, the 2 lateral petals (wings) similar to each other, the 2 lowest petals fused into a keel and enfolding the pistil and stamens; corolla soon drying but persistent. Flowers in small, usually dense heads
Fruit a short pod (legume) often enfolded within persistent calyx, 1-6 seeded.
Origin: all ours from Eurasia or Europe.