Think about the climate of Scotland. Now think about yours. Calluna vulgaris needs cool summer conditions, especially cool roots, bright light but not hot sun, cold winters, ample moisture, but good drainage, and an acid soil. Maintaining these conditions in a pot would be particularly difficult. I should imagine it is totally unsuited to growing in California. It is probably sold as a temporary decoration for nostalgic reasons and, personally, I'd give up on it.

I notice the label says 'likes sun'. This is unhelpful. It likes light certainly but it doesn't like heat.

With a climate most like the UK, heaths and heathers thrive in the PNW. In fact, one of the largest (and only) specialty heather mail order nurseries is located here They are sold everywhere, including box stores and groceries.

One thing I have determined is that they do not tolerate drying out, especially in those small 4" pots. Once well established, they become more drought tolerant but still need some regular moisture in our dry summers.

The brown tips look like drought damage to me.

@floral_uk z.8/9 SW UK These are going into a raised bed with acid-loving plants. I plan on further lowering the pH around the Heath and Heathers. I think the requirement for quite low soil pH alone makes it quite a challenging plant.

Your point on cool roots is taken, and perhaps I can partially address that by using a thicker mulch layer and hiding them behind rocks, to provide a cool area for the roots to expand.

I have them in morning sun and afternoon shade, so I think I have a shot at making this work.

@gardengal48 (PNW Z8/9) 4-inch pots are my nemesis. I routinely take fantastic plants in small pots, and just two days of sun and no water do them in. I am getting better about putting small pots into the shade and checking on water at least every other day.

" I plan on further lowering the pH around the Heath and Heathers. I think the requirement for quite low soil pH alone makes it quite a challenging plant."

I wouldn't worry about pH too much. As long as it tests out at 6.0 - 6.5 or so, the heather will be fine. Calluna vulgaris is not all that demanding about acidic soils.