The violet and pansy family
Violaceae is a small family carrying one very large genus, and almost everything of interest in it happens at ground level. These are low plants with short stems and a set of biological tricks out of all proportion to their size.
around 25 genera
roughly 1,000 species
Worldwide, with Viola concentrated in northern temperate regions
A violet flower is not symmetrical the way a buttercup is. Turn one to face you and it has a left and a right rather than a rotation: two petals standing up, two out to the sides and one hanging below, larger than the rest, doing the work of a landing platform.
That lower petal runs backward into a hollow spur behind the flower, and the spur holds nectar. Two of the five stamens push small appendages into it, so an insect after the nectar has to force its head past the reproductive parts to reach the reward. The markings radiating out from the throat of a pansy are not decoration either. They are nectar guides, lines pointing at the entrance, and under ultraviolet light they are far more pronounced than they look to us.
Pansies are Viola x wittrockiana, a garden hybrid with no wild equivalent, bred up in the nineteenth century from a handful of European species. The name comes from the French pensee, a thought, which is why Ophelia hands out pansies for thoughts.
The violets in flower in spring frequently set no seed at all. Most of the seed a violet produces comes from a second kind of flower altogether, made later in the season, held at or below ground level, small, green, without petals and sealed shut for its entire life. It pollinates itself inside the closed bud and produces a capsule.
This is called cleistogamy, and violets are the standard example. The plant is running two strategies at once: showy flowers that gamble on an insect and produce genetically varied offspring, and closed flowers that cost almost nothing and guarantee seed whatever the weather does.
The dispersal is worth knowing as well. The ripe capsule splits into three boat shaped valves which dry, contract and squeeze the seeds out under pressure, throwing them several feet. Each seed carries an oily appendage that ants find worth carrying home, so the ants take them further still and discard the seed itself unharmed.
Sweet violet has the strangest scent in the flower trade. Smell one and it is unmistakable; keep smelling and within seconds it fades to nothing, and then a moment later it returns. Nothing has changed in the flower.
The compounds responsible are ionones, and they bind to the smell receptors and briefly shut them down. The nose stops registering the scent while the receptors reset, then picks it up again. It is the only common flower that does this, it happens to everybody, and it is the reason violet is described as coming in waves.
Perfumery still uses violet leaf, which smells green and cucumber like rather than floral, but the flower absolute has been effectively unobtainable for a century. Almost every violet perfume is built from synthetic ionones instead, which were among the first commercially important synthetic aroma materials.
Viola holds the great majority of the species here and is the only part of the family most people will ever meet. The remaining genera are largely tropical trees, shrubs and climbers, several of them substantial timber plants, and they do not read as violets at all. Rinorea on its own runs to a few hundred species of forest shrub.
What they share is the flower plan rather than the habit, and even that loosens: many of the tropical members have given up the spur and the lopsidedness and produce small regular flowers instead. The family is a clean demonstration that a family is defined by descent and not by resemblance, and that the temperate violet everybody pictures is the odd specialist rather than the type.
One consequence follows for anyone buying them. Nothing in this family is a long stemmed cut flower, in any genus, anywhere in the world. The short stem is not a shortcoming of the garden violet that breeding might one day fix. It is what the family is.
Most genera in this guide hold a single flower, so they are covered on that flower's own page. One genus in Violaceae holds several and has a page of its own.
