The daisy and sunflower family
Asteraceae is either the largest family of flowering plants on earth or the second largest, depending on which authority is counting and how they treat the orchids. Either way it is enormous, and it is the family a florist handles more of than any other. If you have sold a sunflower, a chrysanthemum, a gerbera or a dahlia this week, you have sold Asteraceae.
around 1,900 genera
somewhere near 32,000 species
Every continent except Antarctica
Everything in this guide that belongs to Asteraceae
The thing that defines this family is a piece of botanical sleight of hand. What looks like a single daisy is not a flower at all. It is a tightly packed head of dozens or hundreds of tiny complete flowers, called florets, sitting together on a shared base and surrounded by green bracts that do the job an ordinary flower's outer petals would.
In a classic daisy there are two kinds. The flat white straps around the edge are ray florets, one flower each. The yellow button in the middle is a dense mass of disc florets, and each of those is another complete flower with its own pollen and its own seed to make. A single sunflower head can carry well over a thousand of them. Pull one apart and you can see the spiral they are packed in.
Not every member shows both kinds. A chrysanthemum bred for the trade is usually all ray florets, which is why it reads as solid petals with no eye. Craspedia is the opposite, a ball of disc florets and nothing else. The family name comes from this arrangement: aster is the Greek for star, which is what the head looks like from above.
Because the head is made of many separate flowers, it does not fail all at once. The outer florets go over while the center is still opening, which is why a spent daisy looks ragged rather than collapsed, and why picking the tired outer petals off a chrysanthemum genuinely buys it another day or two of looking respectable.
It also means the head keeps working after cutting, and working costs water. This family drinks harder than almost anything else in the cooler. Sunflowers are the extreme case and can empty a vase in a day, but gerberas, dahlias and zinnias are all thirsty. Underfilled water is the single most common reason a florist thinks they got a bad box.
The stems are the other half of the story. Many are hollow, soft or hairy, and all three foul water quickly. Dahlias and zinnias turn a vase cloudy faster than any rose. Strip everything below the waterline, change the water rather than topping it up, and the difference is measured in days rather than hours.
Gerberas are the family's problem child. The stem is soft, holds a lot of water and bends toward the light, so a gerbera that stood straight in the bucket can be looking at the floor by morning. They are also prone to an air lock right behind the head. Deep, clean, shallow water is the usual advice: enough to drink, not enough to rot the stem.
Sunflowers have a hairy stem that turns to slime in dirty water, and a head heavy enough to snap a softened neck. Dahlias bruise if you so much as hold them wrong and have among the shortest vase lives here, which is why they are a market flower rather than a shipped one.
At the other end, this family also gives you the best dried material in the business. Craspedia and yarrow hold their color for years rather than days, and strawflower keeps its shape indefinitely. Same family, opposite ends of the shelf life.
Asteraceae is not only a cut flower family. Lettuce is in it, and so are artichokes, endive, chicory and tarragon. So is the sunflower grown for oil rather than for a vase, and safflower, and the wormwood that flavors absinthe and vermouth.
Some of the most persistent weeds in the world are here too. Dandelions, thistles, ragweed and burdock are all built on the same composite head, which is a large part of why they are so successful: hundreds of flowers per head means hundreds of seeds, and many of them come with a parachute.
That reach is worth knowing when somebody says they react to chrysanthemums. Asteraceae sensitivity is a real thing and it tends to run across the family rather than stopping at one species, so a customer who struggles with one member is often better steered to a different family altogether than to another daisy.