Good evening, I have planted several containers over the past couple weeks and I have noticed that some of the plants in them started to develop a purple discoloration of the leaves within a few days of being transplanted. Specifically, the mint and catnip I planted in a large stock watering tank (with drainage holes cut in the bottom), and the sweet potato vine I planted in a pot with some other foliage plants, have developed this discoloration. I have read that it could be any number of things, including too much water, too little water, a phosphorous deficiency, and other things. I have attached some pictures below. It seems that the new growth on the catnip and the mint is coming in with normal color. I added some organic fertilizer to the containers with the herbs last night, but it is obviously too soon to see if that would help the problem. I was also concerned that the stock tanks were placed too close to a SW facing wall of our house, which has white vinyl siding. I thought that the plants were getting scorched from the sun and the reflection of the sun off of the siding. I used Sta-Green potting soil for container gardens, and I don't know if that is a good quality potting soil, or not. It says it has fertilizer included and would feed for up to 9 months. Any thoughts you could share on the situation would be greatly appreciated. Thanks,
Washington County Maryland
We think you are right about the sun. The leaves of the original transplants were not used to so much intense light. Notice in the photos--the first and second ones especially--that the discoloration stops at a line just where shading from a leaf above it begins. That leaf protected the lower one.
This is a common issue when moving plants into locations with differing light levels. The original leaves grew adapted to one light level and reacted to the new light level.
You'll notice that the new leaves are healthy. That's because they are growing adapted to the new light level. They should be fine from here on out.
Thank you very much! I'll be more careful about that the next time I transplant something outside!