The primrose and cyclamen family
Primulaceae is a family of cool places. Its members come off woodland floors, alpine ledges and Mediterranean hillsides that are wet all winter and bake all summer, and very nearly everything that goes wrong with one indoors comes from forgetting that.
around 60 genera
roughly 2,600 species
Widespread across the northern temperate zone, with many species in mountains
Look into the throat of a primrose and one of two things is true. Either a green pinhead sits at the mouth of the tube with the stamens hidden below it, or five anthers fill the mouth with the stigma out of sight beneath them. The first is called a pin flower and the second a thrum, and a single plant makes one form or the other and never both.
Charles Darwin worked out what it is for in 1862. Pollen from a thrum is deposited on a visiting insect at exactly the depth where a pin flower's stigma will collect it, and the reverse holds too, so pollen tends to travel between the two forms rather than within one. The plant has built a mechanical bar against fertilizing itself. The arrangement is called heterostyly, and Primula is the example every textbook reaches for.
None of it needs more than a hand lens, and it is worth showing a customer once. Most people have never noticed that the flowers on the bench come in two different constructions.
A cyclamen flower is built backward. The five petals are sharply reflexed, swept up and away from the mouth so the bloom hangs like a shuttlecock with its nose pointing at the ground, and the stalk is bent over at the top so the flower faces down rather than out.
What happens next is stranger. Once a flower is pollinated its stalk starts to coil, winding into a tight spring that draws the developing seed capsule down onto the soil surface and, in some species, tucks it under the leaf litter, where ants take the seeds away. The whole plant grows from a flat tuber rather than a bulb, and it does not divide or make offsets, which is why a cyclamen is bought as a plant and not raised from a piece of one.
Both of these are sold in winter and both are usually killed by kindness. A cyclamen wants a bright room at somewhere around 50 to 60 degrees Fahrenheit. In a warm living room it stops flowering, yellows and collapses inside a few weeks, and no amount of water will fix it, because the heat is the problem.
Water from below. Stand the pot in a saucer, let it take up what it wants for twenty minutes and pour the rest away. Water tipped into the middle of the plant sits in the crown among the tightly packed leaf bases and rots the top of the tuber, which is the single most common way a cyclamen dies. Primroses forgive more, but want the same cool, bright, evenly moist treatment.
A cyclamen that yellows off in spring is not dead. It is a Mediterranean plant going dormant for a dry summer. Stop watering, keep the tuber dry and cool, and start it again in late summer.
Primula obconica, the German primrose, is one of the most reliable causes of occupational contact dermatitis in the flower trade. The culprit is primin, a compound in the fine hairs on the leaves and stems, and repeated handling sensitizes people who were fine with it for years beforehand. It shows up as an itching, blistering rash across the hands and forearms. Low primin varieties have been bred and are worth asking for, and gloves deal with the rest.
Cyclamen carries a separate problem. The tuber concentrates saponins and is toxic to cats and dogs, while the leaves and flowers are much less so, which means a dog that digs one out of its pot has eaten the dangerous part. Elsewhere in the family sit the scarlet pimpernel, the yellow loosestrifes and the shooting stars, all cool climate plants sharing the same five fused petals.
