Why has my rosemary died?

Elaine Mepham, York, North Yorkshire

Stefan says: You say this death seemed to happen in a very short space of time. You dug it up to check the roots which, although dead, didn’t have any pest infestation. It’s surrounded by perfectly healthy flora and had been growing beautifully. Another rosemary, 1.8m away, is perfectly healthy.

I wish I had a definitive answer. I’ve grown rosemary for many years and currently have a small collection of interesting varieties. I’ve found exactly the same thing to happen occasionally and despite my best investigations, have been unable to find the cause. Sometimes, an individual branch of a rosemary plant will die similarly.

Usually I look for insect or disease damage or physical injury at the base of the stem – not the roots – when an entire plant or branch dies suddenly, so do try looking there.