In article , Jaques
d'Alltrades writes

This year I've added a heather seedling which grew in a tray of other
seeds in potting compost, and I have an interesting grass which I can't
identify, and some tormentil - the cinquefoil connection. Unlike most
Rosacae, tormentil has only four petals.

Even more strangely, Rosa sericea has only 4 petals.

--
Kay
"Do not insult the crocodile until you have crossed the river"