I bought four of these from a reputable nursery and planted in front porch planter box last year. They did very well for months, until (about 2 months ago) I noticed the far-right one was turning black (no political implication intended This spread from R to L until all four plants were completely black or getting that way.
I took them back to the nursery today. They were very nice, examined the plants, looked up info, but came up with no clue as to what was happening. AFAIK, I gave them proper water and they got sun 3/4 day in summer and 1/2 day in "winter".
I was concerned that the soil had been infected, but the other plants seem fine.
Is this too fragile a plant?...Or...? Never saw anything so strange as the R to L progression.
Any clues?
TIA
HB