The evening primrose and fuchsia family
Onagraceae is the family that counts in fours, opens at dusk, and gave biology the word mutation. It also holds the fuchsia and the fireweed, which is a wider spread than a family this size has any right to.
around 22 genera
roughly 650 species
Worldwide, with the great majority in western North America
Everything in this guide that belongs to Onagraceae
Almost nothing in botany is this consistent. Count the parts of any flower in this family and you get four sepals, four petals, eight stamens in two rings of four, a stigma divided four ways and an ovary with four chambers. Where other families wander between five and six and sometimes more, this one holds to its number with remarkable discipline.
The other structure worth knowing is less obvious. Between the top of the ovary and the base of the petals there is often a tube, sometimes very long, and it is not a stalk. The ovary is at the bottom of it and the flower is at the top, so what looks like a slender stem carrying a bloom is partly flower already.
In the evening primroses that tube can be inches long, which is not an accident of growth. It is a measuring device, and what it measures is the tongue of the animal the flower is built for.
Evening primroses open at dusk and they do it fast enough to sit and watch. The sepals let go, the bud unwinds and the flower is fully out inside a few minutes, sometimes in under one. It is one of the few plant movements that happens on a human timescale and it is worth doing once, with a bud that is bulging and pale in the late afternoon.
The timing is for moths. The flowers are pale yellow or white so they hold what light is left, they release a strong sweet scent after dark, and the nectar is at the bottom of that long tube where only a long tongued hawkmoth can reach it. By the middle of the next morning the flower is spent and going limp, having done its work in a single night.
The seeds of these plants are pressed for evening primrose oil, which is grown as a field crop on a serious scale, and the roots of the biennial species were eaten in North America long before anybody was interested in the oil.
Around 1900 the Dutch botanist Hugo de Vries was growing evening primroses and finding something that should not have been happening. Every so often a plant appeared that was clearly and heritably different from its parents, in one jump, with no intermediate stages. He called these sudden inherited changes mutations, and built a whole theory of evolution on them.
De Vries was one of the three people who independently rediscovered Mendel's work, so this was not a crank. The theory was wrong in its large claims, but the word stuck and is now one of the most used terms in biology.
What was actually happening took decades to work out and is stranger than the theory it inspired. These particular plants have their chromosomes joined end to end into rings that segregate as a unit rather than shuffling normally, so entire blocks of inheritance travel together and occasionally break out. It is one of the oddest genetic systems known in plants, and it happened to be sitting in the one genus a founding geneticist chose to study.
Fuchsia is in this family, which surprises people who have only met the bedding kind. The wild species are shrubs and small trees from the Andes and New Zealand, hummingbird pollinated, with the same four part flower hanging on a long tube.
Fireweed is the other famous relative and it is the plant that follows disaster. It colonizes burned ground within a season, which is where the name comes from, and after the bombing of London it came up across the ruins in such quantity that Londoners called it bombweed. Its seeds carry silky plumes and travel for miles.
The genus this site's member belongs to carries the name of William Clark, of the expedition that crossed the continent in 1804. The plants were collected on that journey, brought back east and named for him, which makes a common summer annual a direct souvenir of the survey of the American west.