Almonds, cherries, peaches and plums all grow from one ancient genus
Almonds, apricots, cherries, peaches and plums all belong to one genus, Prunus, a branch of the rose family with about 340 accepted species. Each produces a drupe: soft flesh wrapped around a single hard stone. The fossil trail of that lineage reaches back to British Columbia in the middle Eocene.
Every Prunus fruit follows the same plan. The flowers usually carry five petals and five sepals, white to pink and occasionally red, with many stamens, and they give way to a fleshy drupe holding one large seed in a hard coat. Some species keep their leaves all year, most drop them, and a handful grow spines. The name reached Latin from Greek, and prūnum meant the plum fruit; the Greek word itself probably came from an older language of Asia Minor.
The earliest confirmed fossils, including wood, a drupe, a seed and a leaf, come from the Princeton Chert of British Columbia. Calibrating a family tree against those finds suggests Prunus and the apple subfamily went separate ways about 44.3 million years ago. Sorting the living species has proved harder. Carl Linnaeus spread them across four genera in 1737, then cut that to two in 1758; later botanists folded everything into one genus, because the forms blur into each other so smoothly.
Growers value the group for food, blossom and timber. The almond is not a true nut: what people eat is its seed. Many species are cyanogenic, so a pit that is harmless in one fruit can be poisonous in another. Black cherry wood is prized for furniture in North America, blackthorn makes hedges, and Japan's sakura belong to the flowering cherries. One grafted showpiece, the Tree of 40 Fruit, carries 40 varieties on a single rootstock.
The trees have their troubles. Plums shelter the damson-hop aphid over winter, and it attacks hops just as they ripen, so plum trees are best kept away from hop fields. Stone fruits ooze gum from any wound, a condition called gummosis, and in North America black knot fungus is common enough that cities run programmes to cut out infected branches.
Source: Prunus
