I'm hoping that someone knows what has happened to this primula, which is quite odd in my limited experience.
A year or so ago I planted a very small section of a divided primula next to a log in my front garden, in the semi-shade of my philadelphus.
As it developed and grew new leaves it seemed quite normal at first. After a while I noticed it had developed small hard protuberances on the upper side of the leaves, which developed into a thorny shape. They appeared to 'bursting from the underside of the leaves. These disappeared after some time and as the leaves grew bigger this year, they were longer and more slender than usual for a primula.
As it wasn't developing normally it was always my intention to dig it out, which I did yesterday. It was also smaller than I would expect for the time it had been in the ground. But what I also discovered, which you can see clearly in the photo's is that it had developed small, very sharp and solid small thorns along the under-spine of the leaves, as well as quite a large taproot, neither of which I've ever seen on a primula.
A couple of things that may have affected it are that it was very close to the log and was also very entangled in the fine roots of the philadelphus. In every other respect the leaves and roots looked very healthy. Also it hasn't flowered, whereas the other divided sections have.
Could this be a defensive adaptation to being crowded or some kind of disease?