White clover, Trifolium repens, has, by definition, a trio of leaves. "Trifolium" means "three-leaved" in Latin.
On rare occasions, though, a clover appears with a fourth leaf. Considered by many to be an indicator of luck, it definitely is rare, occurring only once every 10,000 plants. Controlled by a recessive gene, the rare fourth leaf is generally smaller than the other three. Other rare genetic variations in the white clover include red leaf veins and red flecks on the leaves.
Interactions between the plant's genes and the soil pH levels, pollution, and temperature may also contribute to the emergence of a fourth leaf, but scientists have not yet reached firm conclusions on what role those interactions play.
Some people who claim to have found four-leaf clovers have, in fact, misidentified different plants entirely. There are several similarly shaped plants that normally bear four leaves, including pepperwort, water clover, and oxalis, that are commonly confused with white clover.
The most leaves occuring on a single stem of white clover is 56. It was discovered in Hanamaki City, Japan, and is credited to a local clover breeder.
Check out these related Science NetLinks resources on genetics and plants:
- Look at Those Seeds Grow! (K-2)
- What Parts Are There to a Plant? (K-2)
- Nature and Nurture (3-5)
- Plant Hunter (3-8)
- iNaturalist App (3-12)
- Gene Puzzles (6-8)
- Plants 1: Plant Parents (6-8)
- Lookalike Species (6-12)
- Cracking the Genetic Code (9-12)
- Gene Screen App (9-12)
- Genetic Science Learning Center (9-12)
- A Mendel Seminar (9-12)