Question: Earlier this year I bought two very big rosemary bushes and planted them in two big terracotta pots for either side of our front door.
They looked great for a while but are now turning brown at the tips. Also the whole plants are going yellow in patches. What can I do to get them green and healthy again?
Answer: Rosemary has a few pests that bother it, including rosemary beetle and leaf hopper, but none of these fit your description of the damage you describe.
I do wonder whether the plants have become a little on the dry side. Despite its Mediterranean origins, rosemary in containers needs more water than you might think.
When you water, keep going until it comes through the drainage holes - then you know the container is thoroughly soaked. The ideal compost would be a John Innes No 3 with 20% added grit by volume and just pot into container a few centimetres wider all the way round than the original.