In message , Gordon Filby
writes
Hello,

one by one the twigs (correct name?) of my potted rosemary are loosing their
strong green colour and turning pale. I cut out the first of these some
weeks ago and discovered this morning that there are four more. The
remaining twigs look very healthy, but I fear they will turn out similar.

Does anyone know what the cause might be and how to stop it?

Rosemary can be tricky sometimes. There is a fungus that rips through it
very quickly. You should be able to see faint white wool in the leaf
axils on dying stems.

PS I'm resident in Karlsruhe, SW Germany. It has been very hot (30- 35C)
here over recent weeks. The plant is in a shady position (gets filtered
late evening sun) but on the corner of the house where there might be some
turbulence. It has been kept well watered.

I'm not sure, but over watering might be implicated in allowing the
fungi to take hold. Usually its a problem coming out of wet winters. I
have never found anything effective against dying rosemary apart from
pruning out all diseased wood with a huge safety margin and burning it.

Regards,
--
Martin Brown