The leadwort and sea lavender family
Plumbaginaceae lives where almost nothing else will: salt marsh, sea cliff, desert salt pan and mine spoil. It manages it with a piece of equipment very few plant families ever evolved, and everything the flower trade values about it follows from that.
around 27 genera
roughly 900 species
Worldwide on coasts, salt flats and dry steppe
Everything in this guide that belongs to Plumbaginaceae
Salt is a serious problem for a plant. It pulls water out of roots rather than letting it in, and once inside it wrecks the machinery of the cell. Most plants deal with it by simply not growing anywhere salty. This family took the other route and built a way to get rid of it.
Scattered across the leaf surface are salt glands, small multicelled structures that actively pump sodium and chloride out of the plant and onto the outside of the leaf. They run constantly. On a hot dry day the excreted salt dries where it lands, and the leaves of a sea lavender or a thrift can be visibly crusted and gritty with crystals that glitter in the sun and wash off with the next rain.
Only a handful of plant families anywhere solved salt this way. It is the reason this one owns habitats that are otherwise close to empty, and why a salt marsh in late summer can be solidly colored by a plant with no competition in sight.
Salt ground is physiologically a desert. Water may be all around, in the marsh or the sea beside it, but it is not water the plant can easily take up, so everything here is built as though drought were permanent, because functionally it is.
That produces tissue with a low water content, heavily stiffened cell walls and a great deal of structural material for the amount of living matter involved. A plant like that has already done most of the work of being a dried flower while it is still growing in the ground.
This is the real reason the family dominates the dried trade rather than merely appearing in it. Ordinary flowers are mostly water held in shape by pressure, so drying one means collapse and shrinkage and loss of color. These plants have very little to lose in the first place, so they come out of the process nearly unchanged, and they do it whether anybody intended to dry them or not.
The neat pink cushions on sea cliffs across northern Europe are in this family, and they are tough in a second way beyond salt. Thrift grows on the spoil heaps of old lead and copper mines, on ground carrying concentrations of heavy metal that kill most vegetation outright, and populations living on those sites have evolved genuine tolerance over a few hundred years.
That makes the plant useful and interesting to people studying how quickly evolution can work and how contaminated land might be stabilized and revegetated. Mine spoil populations and cliff populations of the same species can differ measurably in what they will survive.
It was familiar enough in Britain to be put on the coinage. The twelve sided threepenny bit carried a head of thrift for decades, which was quietly appropriate for a coin during a period of national economizing.
Sea lavenders are a taxonomic headache and the reason is that a great many of them reproduce by making seed without fertilization. The seed is viable, the offspring are clones of the parent, and pollination has dropped out of the process.
The result is swarms of tiny, stable, self perpetuating populations that differ slightly from one another and never interbreed to average themselves out. Britain alone has a set of these confined to particular stretches of cliff, each occupying a headland or two and found nowhere else, and botanists have argued for a century over how many of them are really species.
The family name is unrelated and comes from lead. One genus was called plumbago either because Pliny reported it as a treatment for lead poisoning or because somebody thought its flowers were the color of the metal, and leadwort is the English version. Neither explanation has ever been settled.