The little blue edible flowers of common blue violet are a welcome sight in our garden in early spring, as my fleuravorous daughter loves to feed the sweet little flowers to our family, passersby, and her miniature menagerie. Most people are familiar with the violet genus (Viola spp., Violaceae), readily identifying the group by their typically heart shaped leaves and distinctive flowers.
However, I would venture to say that most people are not familiar with violets second kind of flowers, which grow hidden underground, never opening their petals to the light of day. These cleistogamous flowers (the root of cleistogamy comes from the Greek words cleistos, which means closed, and gamos, meaning marriage; thus cleistogamy translates to closed marriage) never open to pollinator or breeze, yet produce viable seeds. The white violet cleistogamous flower pictured here will never turn blue, as there is no need to attract a pollinator.
The fruits develop underground and release their seeds directly into the soil or close to the surface. Pictured below are the seeds from a cleistogamous violet flower. Fairies have been known to gather up these iridescent seeds and string them into necklaces, much as humans employ freshwater pearls for adornment.
Cleistogamous flowers are in a closed relationship with themselves (I think I know some two legged mammals liked that) versus the ubiquitous free-loving chasmogamous flowers (open-marriage) that freely share their DNA with many individuals within their species. I never conceptualized the typical flower as such a swinger until I pondered the chastity of the cleistogamous lifestyle. Chasmogamous flowers have evolved as the dominant form of floral reproduction because they favor genetic exchange between members of the species, which ultimately strengthens the diversity within the gene pool.
So why do this cryptic non-gene-pool-strengthening-of questionable-moral-character thing? Because even violets need a plan B! What if slugs come along and eat all your flowers, or a seven-year-old girl picks all your flowers for her mini doll wild foods tea party? Behold the picture below, and you will understand the evolutionary pressures violets have faced for millennia. Are you telling me you wouldn’t make a few hidden flowers when faced with similar danger?
Cleistogamy has evolved independently in many members of unrelated plant families, such as violets (Violaceae), rushes (Juncaceae), legumes (Fabaceae), and grasses (Poaceae). Its easy to spy on the cleistogamous flowers and fruit of the common blue violet (Viola sororia, Violaceae); simply pull away the dirt from the base of a plant in summer or fall and you will see the white or green colored cleistogamous reproductive structures. Break open a precious fruit if you have the heart, and take a close look at the seeds, which bear a little white protruding structure, called an elaiosome. What in the heck is an elaiosome?