The rose family
Rosaceae is the family the whole flower trade is built on, and it is also, improbably, the family that supplies most of the fruit bowl. Roses, cherry blossom and hawthorn sit alongside apples, pears, plums, peaches, strawberries and almonds. Once you know what the flowers have in common, the connection stops being surprising.
around 90 genera
somewhere near 4,800 species
Worldwide, and heavily concentrated in the northern temperate zone
Everything in this guide that belongs to Rosaceae
The basic Rosaceae flower is simple and consistent: five petals, five sepals, and a great many stamens arranged in a ring. Look at an open dog rose, an apple blossom, a strawberry flower and a cherry blossom side by side and they are visibly the same design in different colors and sizes.
The garden rose looks like an exception because it is one. A rose with forty petals is a rose whose stamens have been bred into petals over centuries of selection, a change called doubling. It is why highly bred roses often carry little pollen and less scent: the parts that made both have been converted into the thing the buyer wanted to see.
The other constant is the hypanthium, a cup below the petals that the flower parts sit on. What that cup becomes after flowering is what separates a rose hip from an apple from a strawberry, and it is the single structure that ties the ornamental half of this family to the edible half.
Most cut members here are woody, and woody stems have a specific failure mode. They draw air into the water column readily, and an air lock in a rose stem produces the bent neck every florist recognizes: a flower that looks perfect but folds over at the top because water is not reaching the head.
The answer is a clean angled cut with a sharp blade, made under water or straight into water, and never crushing or hammering the stem. Hammering was standard advice for decades and it is actively harmful, because smashed tissue rots and blocks the very vessels the water has to travel through.
A rose that has already bent can often be saved. Recut it, lay the whole stem flat in cool water for an hour or two so it can take up water along its length, and a surprising number stand back up. It is worth trying before writing off a box.
Cherry blossom, hawthorn and the other flowering branches in this family behave nothing like a rose and should not be treated like one. They are cut in bud from dormant wood, and what you are selling is the opening rather than the flower.
Bring them into warmth and they open over several days. Keep them cool and they hold. That gives real control over timing, which is why blossom is a wedding flower: a branch can be run early or held back by a couple of days with nothing more than a change of room.
The trade-off is that once open, blossom drops. Petals will be on the table within a few days and there is no preventing it, only planning for it. Hawthorn adds a second warning, which is that the scent of the open flower is genuinely unpleasant to many people at close range, and it is not a flower for a dining table however good it looks in the hand.
Apples, pears, quinces, cherries, plums, apricots, peaches, nectarines, almonds, strawberries, raspberries, blackberries and loganberries are all Rosaceae. So is the sloe in a hedgerow, and the rowan, and the medlar. It is one of the most economically important plant families in the world and the flowers are the smaller half of it.
The almond connection explains a scent people notice without placing. Many members carry small amounts of compounds related to hydrogen cyanide in their seeds and bark, which is where the marzipan note in cherry and almond comes from, and why cherry laurel foliage smells of it when crushed. It is also why the pits of stone fruit are not something to chew.
For a florist the useful part of all this is the rose hip, which is simply the family's fruit doing what the rest of the family does, and one of the best pieces of fall material available. Sold as a berry stem, it is the same organ as the apple, built to a different scale.
Most genera in this guide hold a single flower, so they are covered on that flower's own page. One genus in Rosaceae holds several and has a page of its own.