The science of the lucky charm: the four leaf clover

Scientists have now discovered the gene responsible for creating a four-leaf clover, using molecular markers, according to research published in the July/August 2010 edition of Crop Science.

The white clover plant is actually a genetically complex organism. The gene for four leaves is rarely expressed and environmental factors also contribute. So the answer for why four-leaf clovers exist in white clover is a combination of a rare gene and environmental conditions.

It has been hard to discover the gene up until now because it is hidden by the allele for three leaves. The use of molecular markers made the discovery possible.

The variation in white clover trifolium repens. Four-leaf clovers are considered lucky. (Credit: billaday via Flickr)

(NOTE: I decided that since St. Patrick’s day was moved to the 15th, but is generally on the 17th, I would split the difference and post my themed post on the 16th)

Four-leaf clovers: the rare, sought-after variation of the more common three-leaf clover. It is said to be lucky, and indeed, you’d be lucky to find them. Some statistics state that there are 10,000 normal three-leaf clovers to every four-leaf clover.

I somehow think that is a little exaggerated. I myself have found 3 four-leaf clovers in my life time… mostly before I was out of grade school and had plenty of time to gaze at the grass where White clover, Trifolium repens, grew.

Some people try to claim they’ve found a four-leaf clover, but often they have just picked the leaf of a plant that consistently produces four-leaves, such as Pepperwort (Marsilea Quadrifolia) or Oxalis (any variety).

But what causes a true clover to produce this variation? Obviously it is a variation— the scientific name for clover, Trifolium, means three (tres) leaf (folium). A real four-leaf clover also has a fourth leaf that is often smaller than the rest.

The truth of the matter is that scientists are unsure of the exact cause of four-leaf clovers, and indeed, there may be more than one factor causing this variation. However, here is a list of possible causes.

• Environmental:

To suggest an environmental factor, seekers of the lucky leaflet have found that certain patches of clover were more likely to have four-leaf clovers. This occurrence suggests that environmental factors such as soil pH, soil composition, pollution of the area, or other influencing factors. Some suggest that environmental stressors produce more variation, but this is unknown.

• Genetic:

Taking into consideration the rarity of the four-leaf cover, it is possible that the variation is not so much a mutation, but a recessive gene that crops up occasionally. Personally, I think this a little unlikely. I would expect to see a little more four-leaf clovers. There also exist variations with more than four leaves, which is not explained with genetics naming a single gene.

• Mutation:

This one is my favorite possibility for the origin of the four-leaf clover. All multi-cellular organisms have some mutation occurring. Mutation is a fun word, but it is a good thing and creates variation within a population. Mutations are “changes to the nucleotide sequence of the genetic material of an organism.” Basically, a mutated organism is just a little different from its fellows. In four-leaf clovers, the mutation is most likely somatic, meaning the mutation occurs in the somatic cells. Somatic mutations in plants
can sometimes be are not passed down to their offspring. They are mutations that occur after the plant is started.

• All of the above:

It is possible that in some specimens of four-leaf clovers, more than one of these factors contributed to the variation.

Good luck with finding the four-leaf clover.  Most people associate the white clover as the true shamrock, although shamrock simply means “little clover”. Other sources say each of the leaves mean something, like hope, faith, love, and happiness.