I bought three very vigorous tomato plants at Costco and they did well initially but now their leaves are turning a dark reddish purple color. Not wilting or dying, just turning purple. I've never had this happen before. Any ideas?
Certified GKH Gardening Expert
It sounds like the start of a fungal disease, treat it with calcium or a fungicide and you can prune away the bad looking foliage. These articles will help